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	$132.52	13.702%	$150.6779	$150.68	$150.70	$150.70
Purchase #2	$153.48	12.344%	$172.4256	$172.43	$172.45	$172.40
Purchase #3	$74.33	5.563%	$78.465	$78.47	$78.45	$78.50
Purchase #4	$93.81	7.820%	$101.1459	$101.15	$101.15	$101.10
Purchase #5	$65.45	3.104%	$67.4816	$67.48	$67.50	$67.50
Purchase #6	$119.28	3.362%	$123.2902	$123.29	$123.30	$123.30
Purchase #7	$15.97	10.269%	$17.61	$17.61	$17.60	$17.60
7 purchase totals =	$654.84		$711.0962	$711.11	$711.15	$711.10