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	$87.33	4.326%	$91.1079	$91.11	$91.10	$91.10
Purchase #2	$107.55	7.325%	$115.428	$115.43	$115.45	$115.40
Purchase #3	$149.41	9.418%	$163.4814	$163.48	$163.50	$163.50
Purchase #4	$34.49	9.843%	$37.8849	$37.88	$37.90	$37.90
Purchase #5	$53.50	11.360%	$59.5776	$59.58	$59.60	$59.60
Purchase #6	$231.51	13.733%	$263.3033	$263.30	$263.30	$263.30
Purchase #7	$246.51	11.211%	$274.1462	$274.15	$274.15	$274.10
7 purchase totals =	$910.30		$1,004.9293	$1,004.93	$1,005.00	$1,004.90