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	$214.50	4.293%	$223.7085	$223.71	$223.70	$223.70
Purchase #2	$85.29	4.683%	$89.2841	$89.28	$89.30	$89.30
Purchase #3	$86.64	12.388%	$97.373	$97.37	$97.35	$97.40
Purchase #4	$41.52	12.479%	$46.7013	$46.70	$46.70	$46.70
Purchase #5	$68.42	6.591%	$72.9296	$72.93	$72.95	$72.90
Purchase #6	$165.84	7.497%	$178.273	$178.27	$178.25	$178.30
Purchase #7	$64.73	10.657%	$71.6283	$71.63	$71.65	$71.60
7 purchase totals =	$726.94		$779.8978	$779.89	$779.90	$779.90