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	$248.90	10.584%	$275.2436	$275.24	$275.25	$275.20
Purchase #2	$21.72	5.114%	$22.8308	$22.83	$22.85	$22.80
Purchase #3	$192.69	10.335%	$212.6045	$212.60	$212.60	$212.60
Purchase #4	$87.60	13.180%	$99.1457	$99.15	$99.15	$99.10
Purchase #5	$11.71	6.417%	$12.4614	$12.46	$12.45	$12.50
Purchase #6	$96.53	7.753%	$104.014	$104.01	$104.00	$104.00
Purchase #7	$184.51	3.739%	$191.4088	$191.41	$191.40	$191.40
7 purchase totals =	$843.66		$917.7088	$917.70	$917.70	$917.60