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	$94.79	11.827%	$106.0008	$106.00	$106.00	$106.00
Purchase #2	$124.63	9.528%	$136.5047	$136.50	$136.50	$136.50
Purchase #3	$153.70	7.715%	$165.558	$165.56	$165.55	$165.60
Purchase #4	$55.61	7.166%	$59.595	$59.60	$59.60	$59.60
Purchase #5	$41.99	9.676%	$46.053	$46.05	$46.05	$46.10
Purchase #6	$135.61	12.188%	$152.1381	$152.14	$152.15	$152.10
Purchase #7	$243.35	5.413%	$256.5225	$256.52	$256.50	$256.50
7 purchase totals =	$849.68		$922.3721	$922.37	$922.35	$922.40