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	$100.86	10.268%	$111.2163	$111.22	$111.20	$111.20
Purchase #2	$32.65	13.232%	$36.9702	$36.97	$36.95	$37.00
Purchase #3	$10.49	8.110%	$11.3407	$11.34	$11.35	$11.30
Purchase #4	$127.76	7.572%	$137.434	$137.43	$137.45	$137.40
Purchase #5	$29.59	10.374%	$32.6597	$32.66	$32.65	$32.70
Purchase #6	$79.95	11.469%	$89.1195	$89.12	$89.10	$89.10
Purchase #7	$179.96	13.530%	$204.3086	$204.31	$204.30	$204.30
7 purchase totals =	$561.26		$623.0490	$623.05	$623.00	$623.00