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	$211.82	13.497%	$240.4093	$240.41	$240.40	$240.40
Purchase #2	$129.60	8.504%	$140.6212	$140.62	$140.60	$140.60
Purchase #3	$213.68	11.455%	$238.157	$238.16	$238.15	$238.20
Purchase #4	$225.89	3.347%	$233.4505	$233.45	$233.45	$233.50
Purchase #5	$134.96	6.357%	$143.5394	$143.54	$143.55	$143.50
Purchase #6	$159.75	3.576%	$165.4627	$165.46	$165.45	$165.50
Purchase #7	$91.87	11.542%	$102.4736	$102.47	$102.45	$102.50
7 purchase totals =	$1,167.57		$1,264.1137	$1,264.11	$1,264.05	$1,264.20