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	$229.57	10.691%	$254.1133	$254.11	$254.10	$254.10
Purchase #2	$15.55	6.291%	$16.5283	$16.53	$16.55	$16.50
Purchase #3	$230.32	8.810%	$250.6112	$250.61	$250.60	$250.60
Purchase #4	$61.71	4.471%	$64.4691	$64.47	$64.45	$64.50
Purchase #5	$129.51	13.695%	$147.2464	$147.25	$147.25	$147.20
Purchase #6	$225.89	4.548%	$236.1635	$236.16	$236.15	$236.20
Purchase #7	$139.34	13.823%	$158.601	$158.60	$158.60	$158.60
7 purchase totals =	$1,031.89		$1,127.7328	$1,127.73	$1,127.70	$1,127.70