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	$230.84	10.626%	$255.3691	$255.37	$255.35	$255.40
Purchase #2	$119.76	13.665%	$136.1252	$136.13	$136.15	$136.10
Purchase #3	$14.31	8.786%	$15.5673	$15.57	$15.55	$15.60
Purchase #4	$92.65	7.503%	$99.6015	$99.60	$99.60	$99.60
Purchase #5	$38.67	3.117%	$39.8753	$39.88	$39.90	$39.90
Purchase #6	$25.27	4.721%	$26.463	$26.46	$26.45	$26.50
Purchase #7	$200.84	3.717%	$208.3052	$208.31	$208.30	$208.30
7 purchase totals =	$722.34		$781.3066	$781.32	$781.30	$781.40