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	$226.85	11.742%	$253.4867	$253.49	$253.50	$253.50
Purchase #2	$206.47	11.466%	$230.1439	$230.14	$230.15	$230.10
Purchase #3	$59.33	8.779%	$64.5386	$64.54	$64.55	$64.50
Purchase #4	$75.38	3.586%	$78.0831	$78.08	$78.10	$78.10
Purchase #5	$26.71	6.743%	$28.5111	$28.51	$28.50	$28.50
Purchase #6	$55.85	9.782%	$61.3132	$61.31	$61.30	$61.30
Purchase #7	$27.54	12.379%	$30.9492	$30.95	$30.95	$30.90
7 purchase totals =	$678.13		$747.0258	$747.02	$747.05	$746.90