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	$185.90	7.126%	$199.1472	$199.15	$199.15	$199.10
Purchase #2	$216.43	3.158%	$223.2649	$223.26	$223.25	$223.30
Purchase #3	$33.28	8.544%	$36.1234	$36.12	$36.10	$36.10
Purchase #4	$22.35	12.149%	$25.0653	$25.07	$25.05	$25.10
Purchase #5	$48.81	13.718%	$55.5058	$55.51	$55.50	$55.50
Purchase #6	$192.38	4.384%	$200.8139	$200.81	$200.80	$200.80
Purchase #7	$27.67	5.341%	$29.1479	$29.15	$29.15	$29.10
7 purchase totals =	$726.82		$769.0684	$769.07	$769.00	$769.00