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	$38.36	5.760%	$40.5695	$40.57	$40.55	$40.60
Purchase #2	$124.55	11.162%	$138.4523	$138.45	$138.45	$138.50
Purchase #3	$89.43	6.500%	$95.243	$95.24	$95.25	$95.20
Purchase #4	$165.31	11.846%	$184.8926	$184.89	$184.90	$184.90
Purchase #5	$132.51	9.145%	$144.628	$144.63	$144.65	$144.60
Purchase #6	$237.29	5.244%	$249.7335	$249.73	$249.75	$249.70
Purchase #7	$221.31	3.283%	$228.5756	$228.58	$228.60	$228.60
7 purchase totals =	$1,008.76		$1,082.0945	$1,082.09	$1,082.15	$1,082.10