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	$93.60	7.316%	$100.4478	$100.45	$100.45	$100.40
Purchase #2	$170.30	12.246%	$191.1549	$191.15	$191.15	$191.20
Purchase #3	$60.66	9.370%	$66.3438	$66.34	$66.35	$66.30
Purchase #4	$197.78	11.670%	$220.8609	$220.86	$220.85	$220.90
Purchase #5	$119.94	9.299%	$131.0932	$131.09	$131.10	$131.10
Purchase #6	$177.51	11.630%	$198.1544	$198.15	$198.15	$198.20
Purchase #7	$151.75	8.837%	$165.1601	$165.16	$165.15	$165.20
7 purchase totals =	$971.54		$1,073.2151	$1,073.20	$1,073.20	$1,073.30