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	$10.40	10.690%	$11.5118	$11.51	$11.50	$11.50
Purchase #2	$87.66	5.178%	$92.199	$92.20	$92.20	$92.20
Purchase #3	$235.63	6.500%	$250.946	$250.95	$250.95	$250.90
Purchase #4	$133.29	11.346%	$148.4131	$148.41	$148.40	$148.40
Purchase #5	$149.45	11.393%	$166.4768	$166.48	$166.50	$166.50
Purchase #6	$218.91	13.163%	$247.7251	$247.73	$247.75	$247.70
Purchase #7	$199.25	11.646%	$222.4547	$222.45	$222.45	$222.50
7 purchase totals =	$1,034.59		$1,139.7265	$1,139.73	$1,139.75	$1,139.70