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	$34.55	12.741%	$38.952	$38.95	$38.95	$39.00
Purchase #2	$117.43	12.428%	$132.0242	$132.02	$132.00	$132.00
Purchase #3	$212.44	4.743%	$222.516	$222.52	$222.50	$222.50
Purchase #4	$181.28	5.668%	$191.555	$191.56	$191.55	$191.60
Purchase #5	$60.73	10.628%	$67.1844	$67.18	$67.20	$67.20
Purchase #6	$49.48	10.414%	$54.6328	$54.63	$54.65	$54.60
Purchase #7	$47.31	3.178%	$48.8135	$48.81	$48.80	$48.80
7 purchase totals =	$703.22		$755.6779	$755.67	$755.65	$755.70