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	$77.86	6.132%	$82.6344	$82.63	$82.65	$82.60
Purchase #2	$58.47	13.624%	$66.436	$66.44	$66.45	$66.40
Purchase #3	$202.72	10.168%	$223.3326	$223.33	$223.35	$223.30
Purchase #4	$153.73	9.390%	$168.1652	$168.17	$168.15	$168.20
Purchase #5	$130.93	12.804%	$147.6943	$147.69	$147.70	$147.70
Purchase #6	$34.34	6.678%	$36.6332	$36.63	$36.65	$36.60
Purchase #7	$226.95	12.848%	$256.1085	$256.11	$256.10	$256.10
7 purchase totals =	$885.00		$981.0042	$981.00	$981.05	$980.90