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	$177.46	13.154%	$200.8031	$200.80	$200.80	$200.80
Purchase #2	$141.75	13.826%	$161.3484	$161.35	$161.35	$161.30
Purchase #3	$45.33	4.314%	$47.2855	$47.29	$47.30	$47.30
Purchase #4	$122.68	13.712%	$139.5019	$139.50	$139.50	$139.50
Purchase #5	$248.48	13.451%	$281.903	$281.90	$281.90	$281.90
Purchase #6	$165.86	4.105%	$172.6686	$172.67	$172.65	$172.70
Purchase #7	$33.98	12.766%	$38.3179	$38.32	$38.30	$38.30
7 purchase totals =	$935.54		$1,041.8284	$1,041.83	$1,041.80	$1,041.80