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	$96.50	10.457%	$106.591	$106.59	$106.60	$106.60
Purchase #2	$229.98	11.398%	$256.1931	$256.19	$256.20	$256.20
Purchase #3	$223.42	11.678%	$249.511	$249.51	$249.50	$249.50
Purchase #4	$209.92	5.508%	$221.4824	$221.48	$221.50	$221.50
Purchase #5	$247.40	3.666%	$256.4697	$256.47	$256.45	$256.50
Purchase #6	$137.40	11.822%	$153.6434	$153.64	$153.65	$153.60
Purchase #7	$222.86	11.629%	$248.7764	$248.78	$248.80	$248.80
7 purchase totals =	$1,367.48		$1,492.6670	$1,492.66	$1,492.70	$1,492.70