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	$35.44	13.149%	$40.1	$40.10	$40.10	$40.10
Purchase #2	$88.41	9.775%	$97.0521	$97.05	$97.05	$97.10
Purchase #3	$234.55	10.654%	$259.539	$259.54	$259.55	$259.50
Purchase #4	$74.26	7.601%	$79.9045	$79.90	$79.90	$79.90
Purchase #5	$56.82	4.733%	$59.5093	$59.51	$59.50	$59.50
Purchase #6	$59.26	3.157%	$61.1308	$61.13	$61.15	$61.10
Purchase #7	$150.27	5.759%	$158.924	$158.92	$158.90	$158.90
7 purchase totals =	$699.01		$756.1597	$756.15	$756.15	$756.10