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	$193.94	10.141%	$213.6075	$213.61	$213.60	$213.60
Purchase #2	$237.38	7.107%	$254.2506	$254.25	$254.25	$254.30
Purchase #3	$155.99	10.779%	$172.8042	$172.80	$172.80	$172.80
Purchase #4	$243.88	6.831%	$260.5394	$260.54	$260.55	$260.50
Purchase #5	$145.29	10.679%	$160.8055	$160.81	$160.80	$160.80
Purchase #6	$138.43	9.325%	$151.3386	$151.34	$151.35	$151.30
Purchase #7	$113.56	12.283%	$127.5086	$127.51	$127.50	$127.50
7 purchase totals =	$1,228.47		$1,340.8544	$1,340.86	$1,340.85	$1,340.80