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	$59.88	12.609%	$67.4303	$67.43	$67.45	$67.40
Purchase #2	$187.46	13.396%	$212.5721	$212.57	$212.55	$212.60
Purchase #3	$144.46	3.434%	$149.4208	$149.42	$149.40	$149.40
Purchase #4	$132.82	10.386%	$146.6147	$146.61	$146.60	$146.60
Purchase #5	$90.98	10.158%	$100.2217	$100.22	$100.20	$100.20
Purchase #6	$74.99	8.442%	$81.3207	$81.32	$81.30	$81.30
Purchase #7	$224.78	10.584%	$248.5707	$248.57	$248.55	$248.60
7 purchase totals =	$915.37		$1,006.1510	$1,006.14	$1,006.05	$1,006.10