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	$231.88	10.296%	$255.7544	$255.75	$255.75	$255.80
Purchase #2	$214.27	5.230%	$225.4763	$225.48	$225.50	$225.50
Purchase #3	$186.85	7.406%	$200.6881	$200.69	$200.70	$200.70
Purchase #4	$151.39	8.348%	$164.028	$164.03	$164.05	$164.00
Purchase #5	$139.73	11.756%	$156.1567	$156.16	$156.15	$156.20
Purchase #6	$35.61	5.120%	$37.4332	$37.43	$37.45	$37.40
Purchase #7	$64.67	10.238%	$71.2909	$71.29	$71.30	$71.30
7 purchase totals =	$1,024.40		$1,110.8276	$1,110.83	$1,110.90	$1,110.90