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	$130.82	13.262%	$148.1693	$148.17	$148.15	$148.20
Purchase #2	$71.92	7.306%	$77.1745	$77.17	$77.15	$77.20
Purchase #3	$246.73	6.133%	$261.862	$261.86	$261.85	$261.90
Purchase #4	$94.73	6.531%	$100.9168	$100.92	$100.90	$100.90
Purchase #5	$108.31	7.708%	$116.6585	$116.66	$116.65	$116.70
Purchase #6	$38.95	10.636%	$43.0927	$43.09	$43.10	$43.10
Purchase #7	$78.48	12.153%	$88.0177	$88.02	$88.00	$88.00
7 purchase totals =	$769.94		$835.8915	$835.89	$835.80	$836.00