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	$194.80	7.224%	$208.8724	$208.87	$208.85	$208.90
Purchase #2	$20.52	6.680%	$21.8907	$21.89	$21.90	$21.90
Purchase #3	$137.74	9.422%	$150.7179	$150.72	$150.70	$150.70
Purchase #4	$215.98	11.215%	$240.2022	$240.20	$240.20	$240.20
Purchase #5	$114.61	10.221%	$126.3243	$126.32	$126.30	$126.30
Purchase #6	$131.90	13.568%	$149.7962	$149.80	$149.80	$149.80
Purchase #7	$71.39	10.573%	$78.9381	$78.94	$78.95	$78.90
7 purchase totals =	$886.94		$976.7418	$976.74	$976.70	$976.70