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	$106.48	11.274%	$118.4846	$118.48	$118.50	$118.50
Purchase #2	$50.59	7.329%	$54.2977	$54.30	$54.30	$54.30
Purchase #3	$66.44	3.699%	$68.8976	$68.90	$68.90	$68.90
Purchase #4	$64.82	10.562%	$71.6663	$71.67	$71.65	$71.70
Purchase #5	$190.81	9.827%	$209.5609	$209.56	$209.55	$209.60
Purchase #6	$35.47	4.153%	$36.9431	$36.94	$36.95	$36.90
Purchase #7	$15.82	11.182%	$17.589	$17.59	$17.60	$17.60
7 purchase totals =	$530.43		$577.4392	$577.44	$577.45	$577.50