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	$157.46	8.505%	$170.852	$170.85	$170.85	$170.90
Purchase #2	$200.63	8.354%	$217.3906	$217.39	$217.40	$217.40
Purchase #3	$10.75	10.355%	$11.8632	$11.86	$11.85	$11.90
Purchase #4	$13.30	8.795%	$14.4697	$14.47	$14.45	$14.50
Purchase #5	$110.63	13.792%	$125.8881	$125.89	$125.90	$125.90
Purchase #6	$28.48	13.183%	$32.2345	$32.23	$32.25	$32.20
Purchase #7	$119.42	6.733%	$127.4605	$127.46	$127.45	$127.50
7 purchase totals =	$640.67		$700.1586	$700.15	$700.15	$700.30