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	$249.74	10.493%	$275.9452	$275.95	$275.95	$275.90
Purchase #2	$117.57	11.387%	$130.9577	$130.96	$130.95	$131.00
Purchase #3	$214.49	12.577%	$241.4664	$241.47	$241.45	$241.50
Purchase #4	$192.53	10.271%	$212.3048	$212.30	$212.30	$212.30
Purchase #5	$244.53	9.801%	$268.4964	$268.50	$268.50	$268.50
Purchase #6	$98.37	13.521%	$111.6706	$111.67	$111.65	$111.70
Purchase #7	$199.54	9.387%	$218.2708	$218.27	$218.25	$218.30
7 purchase totals =	$1,316.77		$1,459.1119	$1,459.12	$1,459.05	$1,459.20