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	$213.25	11.666%	$238.1277	$238.13	$238.15	$238.10
Purchase #2	$65.45	8.345%	$70.9118	$70.91	$70.90	$70.90
Purchase #3	$66.95	6.566%	$71.3459	$71.35	$71.35	$71.30
Purchase #4	$140.36	9.146%	$153.1973	$153.20	$153.20	$153.20
Purchase #5	$166.69	9.413%	$182.3805	$182.38	$182.40	$182.40
Purchase #6	$128.76	12.344%	$144.6541	$144.65	$144.65	$144.70
Purchase #7	$236.99	8.370%	$256.8261	$256.83	$256.85	$256.80
7 purchase totals =	$1,018.45		$1,117.4434	$1,117.45	$1,117.50	$1,117.40