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	$98.25	13.577%	$111.5894	$111.59	$111.60	$111.60
Purchase #2	$241.35	9.217%	$263.5952	$263.60	$263.60	$263.60
Purchase #3	$59.51	12.770%	$67.1094	$67.11	$67.10	$67.10
Purchase #4	$65.31	13.346%	$74.0263	$74.03	$74.05	$74.00
Purchase #5	$13.83	13.153%	$15.6491	$15.65	$15.65	$15.60
Purchase #6	$242.68	13.478%	$275.3884	$275.39	$275.40	$275.40
Purchase #7	$151.87	3.864%	$157.7383	$157.74	$157.75	$157.70
7 purchase totals =	$872.80		$965.0961	$965.11	$965.15	$965.00