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	$109.77	3.506%	$113.6185	$113.62	$113.60	$113.60
Purchase #2	$32.72	5.851%	$34.6344	$34.63	$34.65	$34.60
Purchase #3	$14.71	5.421%	$15.5074	$15.51	$15.50	$15.50
Purchase #4	$130.81	7.460%	$140.5684	$140.57	$140.55	$140.60
Purchase #5	$32.97	13.655%	$37.4721	$37.47	$37.45	$37.50
Purchase #6	$135.79	12.780%	$153.144	$153.14	$153.15	$153.10
Purchase #7	$63.70	6.593%	$67.8997	$67.90	$67.90	$67.90
7 purchase totals =	$520.47		$562.8445	$562.84	$562.80	$562.80