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	$118.95	9.145%	$129.828	$129.83	$129.85	$129.80
Purchase #2	$153.52	12.388%	$172.5381	$172.54	$172.55	$172.50
Purchase #3	$115.44	7.682%	$124.3081	$124.31	$124.30	$124.30
Purchase #4	$90.86	5.225%	$95.6074	$95.61	$95.60	$95.60
Purchase #5	$104.89	8.476%	$113.7805	$113.78	$113.80	$113.80
Purchase #6	$250.97	13.627%	$285.1697	$285.17	$285.15	$285.20
Purchase #7	$234.85	3.505%	$243.0815	$243.08	$243.10	$243.10
7 purchase totals =	$1,069.48		$1,164.3133	$1,164.32	$1,164.35	$1,164.30