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	$98.34	13.622%	$111.7359	$111.74	$111.75	$111.70
Purchase #2	$231.89	9.851%	$254.7335	$254.73	$254.75	$254.70
Purchase #3	$224.77	7.197%	$240.9467	$240.95	$240.95	$240.90
Purchase #4	$74.50	10.153%	$82.064	$82.06	$82.05	$82.10
Purchase #5	$68.89	5.445%	$72.6411	$72.64	$72.65	$72.60
Purchase #6	$214.85	11.829%	$240.2646	$240.26	$240.25	$240.30
Purchase #7	$164.71	6.763%	$175.8493	$175.85	$175.85	$175.80
7 purchase totals =	$1,077.95		$1,178.2351	$1,178.23	$1,178.25	$1,178.10