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	$203.66	13.375%	$230.8995	$230.90	$230.90	$230.90
Purchase #2	$111.31	4.266%	$116.0585	$116.06	$116.05	$116.10
Purchase #3	$144.60	5.621%	$152.728	$152.73	$152.75	$152.70
Purchase #4	$130.56	12.218%	$146.5118	$146.51	$146.50	$146.50
Purchase #5	$245.36	4.426%	$256.2196	$256.22	$256.20	$256.20
Purchase #6	$56.79	9.201%	$62.0152	$62.02	$62.00	$62.00
Purchase #7	$37.90	3.136%	$39.0885	$39.09	$39.10	$39.10
7 purchase totals =	$930.18		$1,003.5211	$1,003.53	$1,003.50	$1,003.50