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	$177.88	7.246%	$190.7692	$190.77	$190.75	$190.80
Purchase #2	$187.72	11.372%	$209.0675	$209.07	$209.05	$209.10
Purchase #3	$199.56	11.808%	$223.124	$223.12	$223.10	$223.10
Purchase #4	$156.47	13.548%	$177.6686	$177.67	$177.65	$177.70
Purchase #5	$118.26	8.175%	$127.9278	$127.93	$127.95	$127.90
Purchase #6	$135.58	11.739%	$151.4957	$151.50	$151.50	$151.50
Purchase #7	$87.48	5.662%	$92.4331	$92.43	$92.45	$92.40
7 purchase totals =	$1,062.95		$1,172.4859	$1,172.49	$1,172.45	$1,172.50