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	$239.72	3.192%	$247.3719	$247.37	$247.35	$247.40
Purchase #2	$179.48	6.165%	$190.5449	$190.54	$190.55	$190.50
Purchase #3	$54.47	13.250%	$61.6873	$61.69	$61.70	$61.70
Purchase #4	$152.95	11.550%	$170.6157	$170.62	$170.60	$170.60
Purchase #5	$137.84	10.185%	$151.879	$151.88	$151.90	$151.90
Purchase #6	$48.99	11.617%	$54.6812	$54.68	$54.70	$54.70
Purchase #7	$82.26	8.743%	$89.452	$89.45	$89.45	$89.50
7 purchase totals =	$895.71		$966.2320	$966.23	$966.25	$966.30