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	$126.51	3.258%	$130.6317	$130.63	$130.65	$130.60
Purchase #2	$141.67	13.865%	$161.3125	$161.31	$161.30	$161.30
Purchase #3	$204.43	11.801%	$228.5548	$228.55	$228.55	$228.60
Purchase #4	$48.33	12.576%	$54.408	$54.41	$54.40	$54.40
Purchase #5	$50.27	7.105%	$53.8417	$53.84	$53.85	$53.80
Purchase #6	$76.70	10.871%	$85.0381	$85.04	$85.05	$85.00
Purchase #7	$31.39	7.513%	$33.7483	$33.75	$33.75	$33.70
7 purchase totals =	$679.30		$747.5351	$747.53	$747.55	$747.40