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	$72.59	11.325%	$80.8108	$80.81	$80.80	$80.80
Purchase #2	$97.27	7.186%	$104.2598	$104.26	$104.25	$104.30
Purchase #3	$144.98	3.433%	$149.9572	$149.96	$149.95	$150.00
Purchase #4	$146.73	12.497%	$165.0668	$165.07	$165.05	$165.10
Purchase #5	$212.43	5.427%	$223.9586	$223.96	$223.95	$224.00
Purchase #6	$33.29	13.580%	$37.8108	$37.81	$37.80	$37.80
Purchase #7	$247.94	4.496%	$259.0874	$259.09	$259.10	$259.10
7 purchase totals =	$955.23		$1,020.9514	$1,020.96	$1,020.90	$1,021.10