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	$32.96	4.812%	$34.546	$34.55	$34.55	$34.50
Purchase #2	$98.33	13.422%	$111.5279	$111.53	$111.55	$111.50
Purchase #3	$230.74	7.551%	$248.1632	$248.16	$248.15	$248.20
Purchase #4	$124.55	7.327%	$133.6758	$133.68	$133.70	$133.70
Purchase #5	$161.58	7.402%	$173.5402	$173.54	$173.55	$173.50
Purchase #6	$10.48	10.472%	$11.5775	$11.58	$11.60	$11.60
Purchase #7	$173.50	13.191%	$196.3864	$196.39	$196.40	$196.40
7 purchase totals =	$832.14		$909.4170	$909.43	$909.50	$909.40