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	$165.51	8.226%	$179.1249	$179.12	$179.10	$179.10
Purchase #2	$242.48	7.476%	$260.6078	$260.61	$260.60	$260.60
Purchase #3	$249.58	10.354%	$275.4215	$275.42	$275.40	$275.40
Purchase #4	$9.37	8.557%	$10.1718	$10.17	$10.15	$10.20
Purchase #5	$98.41	8.139%	$106.4196	$106.42	$106.40	$106.40
Purchase #6	$92.55	7.388%	$99.3876	$99.39	$99.40	$99.40
Purchase #7	$142.47	6.430%	$151.6308	$151.63	$151.65	$151.60
7 purchase totals =	$1,000.37		$1,082.7640	$1,082.76	$1,082.70	$1,082.70