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	$129.71	13.762%	$147.5607	$147.56	$147.55	$147.60
Purchase #2	$156.40	7.635%	$168.3411	$168.34	$168.35	$168.30
Purchase #3	$238.45	7.642%	$256.6723	$256.67	$256.65	$256.70
Purchase #4	$217.40	9.338%	$237.7008	$237.70	$237.70	$237.70
Purchase #5	$53.89	9.698%	$59.1163	$59.12	$59.10	$59.10
Purchase #6	$141.55	5.561%	$149.4216	$149.42	$149.40	$149.40
Purchase #7	$228.88	11.713%	$255.6887	$255.69	$255.70	$255.70
7 purchase totals =	$1,166.28		$1,274.5015	$1,274.50	$1,274.45	$1,274.50