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	$33.48	13.318%	$37.9389	$37.94	$37.95	$37.90
Purchase #2	$160.71	3.469%	$166.285	$166.29	$166.30	$166.30
Purchase #3	$232.80	7.576%	$250.4369	$250.44	$250.45	$250.40
Purchase #4	$141.96	9.483%	$155.4221	$155.42	$155.40	$155.40
Purchase #5	$151.76	11.616%	$169.3884	$169.39	$169.40	$169.40
Purchase #6	$125.82	11.840%	$140.7171	$140.72	$140.70	$140.70
Purchase #7	$126.63	11.502%	$141.195	$141.20	$141.20	$141.20
7 purchase totals =	$973.16		$1,061.3834	$1,061.40	$1,061.40	$1,061.30