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	$65.32	8.802%	$71.0695	$71.07	$71.05	$71.10
Purchase #2	$192.60	11.797%	$215.321	$215.32	$215.30	$215.30
Purchase #3	$227.65	10.555%	$251.6785	$251.68	$251.70	$251.70
Purchase #4	$105.59	4.476%	$110.3162	$110.32	$110.30	$110.30
Purchase #5	$71.77	9.415%	$78.5271	$78.53	$78.55	$78.50
Purchase #6	$155.67	3.702%	$161.4329	$161.43	$161.45	$161.40
Purchase #7	$37.26	13.411%	$42.2569	$42.26	$42.25	$42.30
7 purchase totals =	$855.86		$930.6021	$930.61	$930.60	$930.60