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	$111.86	12.588%	$125.9409	$125.94	$125.95	$125.90
Purchase #2	$64.82	5.834%	$68.6016	$68.60	$68.60	$68.60
Purchase #3	$133.27	9.130%	$145.4376	$145.44	$145.45	$145.40
Purchase #4	$29.67	13.227%	$33.5945	$33.59	$33.60	$33.60
Purchase #5	$143.79	5.313%	$151.4296	$151.43	$151.45	$151.40
Purchase #6	$28.60	12.191%	$32.0866	$32.09	$32.10	$32.10
Purchase #7	$59.49	13.700%	$67.6401	$67.64	$67.65	$67.60
7 purchase totals =	$571.50		$624.7309	$624.73	$624.80	$624.60