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	$216.25	10.325%	$238.5778	$238.58	$238.60	$238.60
Purchase #2	$144.45	11.673%	$161.3116	$161.31	$161.30	$161.30
Purchase #3	$68.98	13.563%	$78.3358	$78.34	$78.35	$78.30
Purchase #4	$100.32	10.197%	$110.5496	$110.55	$110.55	$110.50
Purchase #5	$210.66	9.105%	$229.8406	$229.84	$229.85	$229.80
Purchase #6	$118.35	5.202%	$124.5066	$124.51	$124.50	$124.50
Purchase #7	$124.34	3.290%	$128.4308	$128.43	$128.45	$128.40
7 purchase totals =	$983.35		$1,071.5528	$1,071.56	$1,071.60	$1,071.40