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	$214.68	5.469%	$226.4208	$226.42	$226.40	$226.40
Purchase #2	$10.57	11.208%	$11.7547	$11.75	$11.75	$11.80
Purchase #3	$156.70	8.760%	$170.4269	$170.43	$170.45	$170.40
Purchase #4	$148.34	13.434%	$168.268	$168.27	$168.25	$168.30
Purchase #5	$188.57	10.634%	$208.6225	$208.62	$208.60	$208.60
Purchase #6	$34.98	6.139%	$37.1274	$37.13	$37.15	$37.10
Purchase #7	$160.37	12.820%	$180.9294	$180.93	$180.95	$180.90
7 purchase totals =	$914.21		$1,003.5497	$1,003.55	$1,003.55	$1,003.50