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	$230.45	13.157%	$260.7703	$260.77	$260.75	$260.80
Purchase #2	$207.39	7.385%	$222.7058	$222.71	$222.70	$222.70
Purchase #3	$192.72	4.270%	$200.9491	$200.95	$200.95	$200.90
Purchase #4	$150.51	3.472%	$155.7357	$155.74	$155.75	$155.70
Purchase #5	$16.44	10.492%	$18.1649	$18.16	$18.15	$18.20
Purchase #6	$128.39	7.252%	$137.7008	$137.70	$137.70	$137.70
Purchase #7	$105.55	12.635%	$118.8862	$118.89	$118.90	$118.90
7 purchase totals =	$1,031.45		$1,114.9128	$1,114.92	$1,114.90	$1,114.90