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	$225.55	13.576%	$256.1707	$256.17	$256.15	$256.20
Purchase #2	$241.32	4.232%	$251.5327	$251.53	$251.55	$251.50
Purchase #3	$225.91	9.284%	$246.8835	$246.88	$246.90	$246.90
Purchase #4	$217.51	11.118%	$241.6928	$241.69	$241.70	$241.70
Purchase #5	$53.59	4.249%	$55.867	$55.87	$55.85	$55.90
Purchase #6	$243.94	4.342%	$254.5319	$254.53	$254.55	$254.50
Purchase #7	$53.88	10.523%	$59.5498	$59.55	$59.55	$59.50
7 purchase totals =	$1,261.70		$1,366.2284	$1,366.22	$1,366.25	$1,366.20