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	$104.83	5.783%	$110.8923	$110.89	$110.90	$110.90
Purchase #2	$55.90	11.258%	$62.1932	$62.19	$62.20	$62.20
Purchase #3	$168.27	13.552%	$191.074	$191.07	$191.05	$191.10
Purchase #4	$223.52	13.754%	$254.2629	$254.26	$254.25	$254.30
Purchase #5	$50.30	6.388%	$53.5132	$53.51	$53.50	$53.50
Purchase #6	$168.45	6.644%	$179.6418	$179.64	$179.65	$179.60
Purchase #7	$174.68	9.344%	$191.0021	$191.00	$191.00	$191.00
7 purchase totals =	$945.95		$1,042.5795	$1,042.56	$1,042.55	$1,042.60