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	$105.74	7.733%	$113.9169	$113.92	$113.90	$113.90
Purchase #2	$149.78	12.503%	$168.507	$168.51	$168.50	$168.50
Purchase #3	$233.90	11.144%	$259.9658	$259.97	$259.95	$260.00
Purchase #4	$55.65	4.102%	$57.9328	$57.93	$57.95	$57.90
Purchase #5	$134.86	11.621%	$150.5321	$150.53	$150.55	$150.50
Purchase #6	$106.27	9.297%	$116.1499	$116.15	$116.15	$116.10
Purchase #7	$144.81	3.724%	$150.2027	$150.20	$150.20	$150.20
7 purchase totals =	$931.01		$1,017.2072	$1,017.21	$1,017.20	$1,017.10