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	$93.43	13.382%	$105.9328	$105.93	$105.95	$105.90
Purchase #2	$30.63	6.261%	$32.5477	$32.55	$32.55	$32.50
Purchase #3	$93.60	12.512%	$105.3112	$105.31	$105.30	$105.30
Purchase #4	$161.93	8.619%	$175.8867	$175.89	$175.90	$175.90
Purchase #5	$152.39	12.643%	$171.6567	$171.66	$171.65	$171.70
Purchase #6	$247.37	7.684%	$266.3779	$266.38	$266.40	$266.40
Purchase #7	$80.41	10.325%	$88.7123	$88.71	$88.70	$88.70
7 purchase totals =	$859.76		$946.4253	$946.43	$946.45	$946.40