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	$106.59	7.680%	$114.7761	$114.78	$114.80	$114.80
Purchase #2	$199.76	12.710%	$225.1495	$225.15	$225.15	$225.10
Purchase #3	$65.84	11.672%	$73.5248	$73.52	$73.50	$73.50
Purchase #4	$133.81	13.405%	$151.7472	$151.75	$151.75	$151.70
Purchase #5	$36.99	6.472%	$39.384	$39.38	$39.40	$39.40
Purchase #6	$62.71	7.816%	$67.6114	$67.61	$67.60	$67.60
Purchase #7	$29.51	13.105%	$33.3773	$33.38	$33.40	$33.40
7 purchase totals =	$635.21		$705.5703	$705.57	$705.60	$705.50