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	$121.83	10.500%	$134.6222	$134.62	$134.60	$134.60
Purchase #2	$93.50	6.433%	$99.5149	$99.51	$99.50	$99.50
Purchase #3	$42.42	7.725%	$45.6969	$45.70	$45.70	$45.70
Purchase #4	$67.45	13.628%	$76.6421	$76.64	$76.65	$76.60
Purchase #5	$189.82	5.678%	$200.598	$200.60	$200.60	$200.60
Purchase #6	$138.61	5.808%	$146.6605	$146.66	$146.65	$146.70
Purchase #7	$129.91	7.770%	$140.004	$140.00	$140.00	$140.00
7 purchase totals =	$783.54		$843.7386	$843.73	$843.70	$843.70