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	$135.62	12.708%	$152.8546	$152.85	$152.85	$152.90
Purchase #2	$174.60	7.808%	$188.2328	$188.23	$188.25	$188.20
Purchase #3	$81.59	13.310%	$92.4496	$92.45	$92.45	$92.40
Purchase #4	$60.68	3.226%	$62.6375	$62.64	$62.65	$62.60
Purchase #5	$70.29	10.808%	$77.8869	$77.89	$77.90	$77.90
Purchase #6	$100.97	4.758%	$105.7742	$105.77	$105.75	$105.80
Purchase #7	$206.79	7.353%	$221.9953	$222.00	$222.00	$222.00
7 purchase totals =	$830.54		$901.8309	$901.83	$901.85	$901.80