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	$67.52	12.694%	$76.091	$76.09	$76.10	$76.10
Purchase #2	$37.51	13.391%	$42.533	$42.53	$42.55	$42.50
Purchase #3	$74.45	12.248%	$83.5686	$83.57	$83.55	$83.60
Purchase #4	$215.51	12.225%	$241.8561	$241.86	$241.85	$241.90
Purchase #5	$57.62	13.188%	$65.2189	$65.22	$65.20	$65.20
Purchase #6	$7.32	5.162%	$7.6979	$7.70	$7.70	$7.70
Purchase #7	$166.29	12.250%	$186.6605	$186.66	$186.65	$186.70
7 purchase totals =	$626.22		$703.6260	$703.63	$703.60	$703.70