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	$91.34	4.105%	$95.0895	$95.09	$95.10	$95.10
Purchase #2	$82.28	3.834%	$85.4346	$85.43	$85.45	$85.40
Purchase #3	$46.39	4.580%	$48.5147	$48.51	$48.50	$48.50
Purchase #4	$40.29	6.574%	$42.9387	$42.94	$42.95	$42.90
Purchase #5	$166.96	3.442%	$172.7068	$172.71	$172.70	$172.70
Purchase #6	$203.95	9.198%	$222.7093	$222.71	$222.70	$222.70
Purchase #7	$166.55	9.773%	$182.8269	$182.83	$182.85	$182.80
7 purchase totals =	$797.76		$850.2205	$850.22	$850.25	$850.10