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	$134.82	4.587%	$141.0042	$141.00	$141.00	$141.00
Purchase #2	$37.70	8.548%	$40.9226	$40.92	$40.90	$40.90
Purchase #3	$17.58	10.159%	$19.366	$19.37	$19.35	$19.40
Purchase #4	$37.47	8.579%	$40.6846	$40.68	$40.70	$40.70
Purchase #5	$219.58	11.318%	$244.4321	$244.43	$244.45	$244.40
Purchase #6	$64.28	11.420%	$71.6208	$71.62	$71.60	$71.60
Purchase #7	$156.98	5.682%	$165.8996	$165.90	$165.90	$165.90
7 purchase totals =	$668.41		$723.9299	$723.92	$723.90	$723.90