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	$33.70	6.374%	$35.848	$35.85	$35.85	$35.80
Purchase #2	$228.62	11.853%	$255.7183	$255.72	$255.70	$255.70
Purchase #3	$172.47	13.370%	$195.5292	$195.53	$195.55	$195.50
Purchase #4	$163.92	6.103%	$173.924	$173.92	$173.90	$173.90
Purchase #5	$37.80	12.469%	$42.5133	$42.51	$42.50	$42.50
Purchase #6	$37.74	7.864%	$40.7079	$40.71	$40.70	$40.70
Purchase #7	$190.61	12.619%	$214.6631	$214.66	$214.65	$214.70
7 purchase totals =	$864.86		$958.9038	$958.90	$958.85	$958.80