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	$150.62	11.613%	$168.1115	$168.11	$168.10	$168.10
Purchase #2	$49.92	9.712%	$54.7682	$54.77	$54.75	$54.80
Purchase #3	$36.68	12.680%	$41.331	$41.33	$41.35	$41.30
Purchase #4	$89.65	12.260%	$100.6411	$100.64	$100.65	$100.60
Purchase #5	$54.33	13.112%	$61.4537	$61.45	$61.45	$61.50
Purchase #6	$15.43	11.856%	$17.2594	$17.26	$17.25	$17.30
Purchase #7	$121.55	7.851%	$131.0929	$131.09	$131.10	$131.10
7 purchase totals =	$518.18		$574.6578	$574.65	$574.65	$574.70