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	$40.87	9.203%	$44.6313	$44.63	$44.65	$44.60
Purchase #2	$117.84	11.682%	$131.6061	$131.61	$131.60	$131.60
Purchase #3	$28.86	8.140%	$31.2092	$31.21	$31.20	$31.20
Purchase #4	$142.27	4.138%	$148.1571	$148.16	$148.15	$148.20
Purchase #5	$73.58	13.794%	$83.7296	$83.73	$83.75	$83.70
Purchase #6	$41.82	9.680%	$45.8682	$45.87	$45.85	$45.90
Purchase #7	$151.96	13.420%	$172.353	$172.35	$172.35	$172.40
7 purchase totals =	$597.20		$657.5545	$657.56	$657.55	$657.60