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	$85.37	11.814%	$95.4556	$95.46	$95.45	$95.50
Purchase #2	$130.91	12.263%	$146.9635	$146.96	$146.95	$147.00
Purchase #3	$18.26	13.569%	$20.7377	$20.74	$20.75	$20.70
Purchase #4	$229.54	5.588%	$242.3667	$242.37	$242.35	$242.40
Purchase #5	$103.89	8.200%	$112.409	$112.41	$112.40	$112.40
Purchase #6	$173.51	9.775%	$190.4706	$190.47	$190.45	$190.50
Purchase #7	$168.80	9.286%	$184.4748	$184.47	$184.45	$184.50
7 purchase totals =	$910.28		$992.8779	$992.88	$992.80	$993.00