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	$187.86	4.665%	$196.6237	$196.62	$196.60	$196.60
Purchase #2	$36.51	8.403%	$39.5779	$39.58	$39.60	$39.60
Purchase #3	$125.46	3.728%	$130.1371	$130.14	$130.15	$130.10
Purchase #4	$250.38	10.146%	$275.7836	$275.78	$275.80	$275.80
Purchase #5	$159.60	8.106%	$172.5372	$172.54	$172.55	$172.50
Purchase #6	$8.44	11.318%	$9.3952	$9.40	$9.40	$9.40
Purchase #7	$111.72	13.807%	$127.1452	$127.15	$127.15	$127.10
7 purchase totals =	$879.97		$951.1999	$951.21	$951.25	$951.10