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	$31.29	10.240%	$34.4941	$34.49	$34.50	$34.50
Purchase #2	$172.86	10.253%	$190.5833	$190.58	$190.60	$190.60
Purchase #3	$134.85	6.689%	$143.8701	$143.87	$143.85	$143.90
Purchase #4	$232.85	10.124%	$256.4237	$256.42	$256.40	$256.40
Purchase #5	$225.85	8.833%	$245.7993	$245.80	$245.80	$245.80
Purchase #6	$94.47	6.459%	$100.5718	$100.57	$100.55	$100.60
Purchase #7	$78.63	3.519%	$81.397	$81.40	$81.40	$81.40
7 purchase totals =	$970.80		$1,053.1393	$1,053.13	$1,053.10	$1,053.20