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	$200.75	8.247%	$217.3059	$217.31	$217.30	$217.30
Purchase #2	$201.94	10.294%	$222.7277	$222.73	$222.75	$222.70
Purchase #3	$53.43	10.865%	$59.2352	$59.24	$59.25	$59.20
Purchase #4	$44.67	13.757%	$50.8153	$50.82	$50.80	$50.80
Purchase #5	$211.70	10.238%	$233.3738	$233.37	$233.35	$233.40
Purchase #6	$102.68	7.733%	$110.6202	$110.62	$110.60	$110.60
Purchase #7	$235.89	5.630%	$249.1706	$249.17	$249.15	$249.20
7 purchase totals =	$1,051.06		$1,143.2487	$1,143.26	$1,143.20	$1,143.20