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	$201.65	7.259%	$216.2878	$216.29	$216.30	$216.30
Purchase #2	$78.89	5.237%	$83.0215	$83.02	$83.00	$83.00
Purchase #3	$106.54	12.762%	$120.1366	$120.14	$120.15	$120.10
Purchase #4	$201.63	11.848%	$225.5191	$225.52	$225.50	$225.50
Purchase #5	$63.78	13.142%	$72.162	$72.16	$72.15	$72.20
Purchase #6	$104.89	8.525%	$113.8319	$113.83	$113.85	$113.80
Purchase #7	$220.85	7.547%	$237.5175	$237.52	$237.50	$237.50
7 purchase totals =	$978.23		$1,068.4764	$1,068.48	$1,068.45	$1,068.40