Anti-aliased Nearest Neighbor Filtering.

NearlyNearestNeighborFiltering.glsl

uniform sampler2D texture;
uniform vec2 textureSize;

varying vec2 uv;

void main(){
	vec2 puv = uv*textureSize;
	
	vec2 hfw = fwidth(puv)/2.0;
	vec2 fl = floor(puv - 0.5) + 0.5;
	
	vec2 nnn = (fl + smoothstep(0.5 - hfw, 0.5 + hfw, puv - fl))/textureSize;
	gl_FragColor = texture2D(texture, nnn);
}