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	$52.43	12.555%	$59.0126	$59.01	$59.00	$59.00
Purchase #2	$64.73	11.375%	$72.093	$72.09	$72.10	$72.10
Purchase #3	$155.77	9.181%	$170.0712	$170.07	$170.05	$170.10
Purchase #4	$76.30	9.513%	$83.5584	$83.56	$83.55	$83.60
Purchase #5	$139.71	12.821%	$157.6222	$157.62	$157.60	$157.60
Purchase #6	$40.91	8.757%	$44.4925	$44.49	$44.50	$44.50
Purchase #7	$205.65	5.407%	$216.7695	$216.77	$216.75	$216.80
7 purchase totals =	$735.50		$803.6194	$803.61	$803.55	$803.70