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	$200.87	11.319%	$223.6065	$223.61	$223.60	$223.60
Purchase #2	$37.71	6.741%	$40.252	$40.25	$40.25	$40.30
Purchase #3	$102.46	8.655%	$111.3279	$111.33	$111.35	$111.30
Purchase #4	$173.45	8.761%	$188.646	$188.65	$188.65	$188.60
Purchase #5	$55.38	6.719%	$59.101	$59.10	$59.10	$59.10
Purchase #6	$36.58	11.868%	$40.9213	$40.92	$40.90	$40.90
Purchase #7	$12.75	7.217%	$13.6702	$13.67	$13.65	$13.70
7 purchase totals =	$619.20		$677.5249	$677.53	$677.50	$677.50