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	$180.38	12.721%	$203.3261	$203.33	$203.35	$203.30
Purchase #2	$40.55	12.211%	$45.5016	$45.50	$45.50	$45.50
Purchase #3	$244.38	4.702%	$255.8707	$255.87	$255.85	$255.90
Purchase #4	$120.74	6.779%	$128.925	$128.93	$128.95	$128.90
Purchase #5	$175.52	9.202%	$191.6714	$191.67	$191.65	$191.70
Purchase #6	$60.45	9.350%	$66.1021	$66.10	$66.10	$66.10
Purchase #7	$137.63	13.212%	$155.8137	$155.81	$155.80	$155.80
7 purchase totals =	$959.65		$1,047.2106	$1,047.21	$1,047.20	$1,047.20