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	$116.75	3.243%	$120.5362	$120.54	$120.55	$120.50
Purchase #2	$6.72	12.468%	$7.5578	$7.56	$7.55	$7.60
Purchase #3	$154.93	10.514%	$171.2193	$171.22	$171.20	$171.20
Purchase #4	$240.89	9.449%	$263.6517	$263.65	$263.65	$263.70
Purchase #5	$11.43	11.363%	$12.7288	$12.73	$12.75	$12.70
Purchase #6	$240.95	6.467%	$256.5322	$256.53	$256.55	$256.50
Purchase #7	$151.58	8.367%	$164.2627	$164.26	$164.25	$164.30
7 purchase totals =	$923.25		$996.4887	$996.49	$996.50	$996.50