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	$149.34	11.732%	$166.8606	$166.86	$166.85	$166.90
Purchase #2	$34.25	13.606%	$38.9101	$38.91	$38.90	$38.90
Purchase #3	$220.28	12.185%	$247.1211	$247.12	$247.10	$247.10
Purchase #4	$208.51	6.610%	$222.2925	$222.29	$222.30	$222.30
Purchase #5	$45.26	11.678%	$50.5455	$50.55	$50.55	$50.50
Purchase #6	$139.92	4.584%	$146.3339	$146.33	$146.35	$146.30
Purchase #7	$168.47	11.636%	$188.0732	$188.07	$188.05	$188.10
7 purchase totals =	$966.03		$1,060.1369	$1,060.13	$1,060.10	$1,060.10