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	$47.36	6.447%	$50.4133	$50.41	$50.40	$50.40
Purchase #2	$130.70	8.228%	$141.454	$141.45	$141.45	$141.50
Purchase #3	$159.93	8.691%	$173.8295	$173.83	$173.85	$173.80
Purchase #4	$219.77	10.619%	$243.1074	$243.11	$243.10	$243.10
Purchase #5	$142.27	7.118%	$152.3968	$152.40	$152.40	$152.40
Purchase #6	$234.96	9.180%	$256.5293	$256.53	$256.55	$256.50
Purchase #7	$13.51	7.813%	$14.5655	$14.57	$14.55	$14.60
7 purchase totals =	$948.50		$1,032.2958	$1,032.30	$1,032.30	$1,032.30