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	$58.40	5.233%	$61.4561	$61.46	$61.45	$61.50
Purchase #2	$238.34	9.579%	$261.1706	$261.17	$261.15	$261.20
Purchase #3	$223.35	3.249%	$230.6066	$230.61	$230.60	$230.60
Purchase #4	$16.55	13.116%	$18.7207	$18.72	$18.70	$18.70
Purchase #5	$18.87	11.648%	$21.068	$21.07	$21.05	$21.10
Purchase #6	$86.39	5.354%	$91.0153	$91.02	$91.00	$91.00
Purchase #7	$59.26	13.682%	$67.368	$67.37	$67.35	$67.40
7 purchase totals =	$701.16		$751.4053	$751.42	$751.30	$751.50