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	$94.49	9.750%	$103.7028	$103.70	$103.70	$103.70
Purchase #2	$37.67	9.790%	$41.3579	$41.36	$41.35	$41.40
Purchase #3	$90.49	10.680%	$100.1543	$100.15	$100.15	$100.20
Purchase #4	$247.69	5.443%	$261.1718	$261.17	$261.15	$261.20
Purchase #5	$195.95	6.362%	$208.4163	$208.42	$208.40	$208.40
Purchase #6	$20.50	9.572%	$22.4623	$22.46	$22.45	$22.50
Purchase #7	$53.67	10.410%	$59.257	$59.26	$59.25	$59.30
7 purchase totals =	$740.46		$796.5224	$796.52	$796.45	$796.70