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	$224.80	7.296%	$241.2014	$241.20	$241.20	$241.20
Purchase #2	$37.37	5.540%	$39.4403	$39.44	$39.45	$39.40
Purchase #3	$82.28	7.333%	$88.3136	$88.31	$88.30	$88.30
Purchase #4	$78.49	5.829%	$83.0652	$83.07	$83.05	$83.10
Purchase #5	$59.46	8.255%	$64.3684	$64.37	$64.35	$64.40
Purchase #6	$57.38	6.749%	$61.2526	$61.25	$61.25	$61.30
Purchase #7	$30.54	13.260%	$34.5896	$34.59	$34.60	$34.60
7 purchase totals =	$570.32		$612.2311	$612.23	$612.20	$612.30