Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.90	11.540%	$150.4675	$150.47	$150.45	$150.50
Purchase #2	$146.65	9.217%	$160.1667	$160.17	$160.15	$160.20
Purchase #3	$29.84	12.285%	$33.5058	$33.51	$33.50	$33.50
Purchase #4	$39.42	12.373%	$44.2974	$44.30	$44.30	$44.30
Purchase #5	$153.68	11.568%	$171.4577	$171.46	$171.45	$171.50
Purchase #6	$188.45	4.289%	$196.5326	$196.53	$196.55	$196.50
Purchase #7	$161.81	5.602%	$170.8746	$170.87	$170.85	$170.90
7 purchase totals =	$854.75		$927.3023	$927.31	$927.25	$927.40