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	$40.25	13.827%	$45.8154	$45.82	$45.80	$45.80
Purchase #2	$50.45	3.448%	$52.1895	$52.19	$52.20	$52.20
Purchase #3	$61.49	9.364%	$67.2479	$67.25	$67.25	$67.20
Purchase #4	$30.82	5.290%	$32.4504	$32.45	$32.45	$32.50
Purchase #5	$14.83	13.488%	$16.8303	$16.83	$16.85	$16.80
Purchase #6	$69.64	4.190%	$72.5579	$72.56	$72.55	$72.60
Purchase #7	$105.85	6.348%	$112.5694	$112.57	$112.55	$112.60
7 purchase totals =	$373.33		$399.6608	$399.67	$399.65	$399.70