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	$175.43	5.230%	$184.605	$184.61	$184.60	$184.60
Purchase #2	$100.54	10.872%	$111.4707	$111.47	$111.45	$111.50
Purchase #3	$125.37	4.745%	$131.3188	$131.32	$131.30	$131.30
Purchase #4	$146.70	6.184%	$155.7719	$155.77	$155.75	$155.80
Purchase #5	$13.52	13.710%	$15.3736	$15.37	$15.35	$15.40
Purchase #6	$233.45	7.627%	$251.2552	$251.26	$251.25	$251.30
Purchase #7	$88.46	12.464%	$99.4857	$99.49	$99.50	$99.50
7 purchase totals =	$883.47		$949.2809	$949.29	$949.20	$949.40