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	$203.89	7.599%	$219.3836	$219.38	$219.40	$219.40
Purchase #2	$160.78	7.138%	$172.2565	$172.26	$172.25	$172.30
Purchase #3	$179.68	11.503%	$200.3486	$200.35	$200.35	$200.30
Purchase #4	$193.30	9.821%	$212.284	$212.28	$212.30	$212.30
Purchase #5	$247.70	3.285%	$255.8369	$255.84	$255.85	$255.80
Purchase #6	$35.42	12.762%	$39.9403	$39.94	$39.95	$39.90
Purchase #7	$199.99	4.255%	$208.4996	$208.50	$208.50	$208.50
7 purchase totals =	$1,220.76		$1,308.5495	$1,308.55	$1,308.60	$1,308.50