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	$173.55	8.558%	$188.4024	$188.40	$188.40	$188.40
Purchase #2	$174.55	10.389%	$192.684	$192.68	$192.70	$192.70
Purchase #3	$34.69	5.543%	$36.6129	$36.61	$36.60	$36.60
Purchase #4	$87.66	13.217%	$99.246	$99.25	$99.25	$99.20
Purchase #5	$140.37	9.290%	$153.4104	$153.41	$153.40	$153.40
Purchase #6	$81.43	11.441%	$90.7464	$90.75	$90.75	$90.70
Purchase #7	$35.89	13.287%	$40.6587	$40.66	$40.65	$40.70
7 purchase totals =	$728.14		$801.7608	$801.76	$801.75	$801.70