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	$129.29	9.784%	$141.9397	$141.94	$141.95	$141.90
Purchase #2	$43.66	8.841%	$47.52	$47.52	$47.50	$47.50
Purchase #3	$10.80	3.341%	$11.1608	$11.16	$11.15	$11.20
Purchase #4	$70.43	11.785%	$78.7302	$78.73	$78.75	$78.70
Purchase #5	$117.48	4.843%	$123.1696	$123.17	$123.15	$123.20
Purchase #6	$139.97	5.342%	$147.4472	$147.45	$147.45	$147.40
Purchase #7	$110.63	4.567%	$115.6825	$115.68	$115.70	$115.70
7 purchase totals =	$622.26		$665.6500	$665.65	$665.65	$665.60