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	$113.25	3.202%	$116.8763	$116.88	$116.90	$116.90
Purchase #2	$135.49	3.675%	$140.4693	$140.47	$140.45	$140.50
Purchase #3	$141.56	6.691%	$151.0318	$151.03	$151.05	$151.00
Purchase #4	$89.42	12.782%	$100.8497	$100.85	$100.85	$100.80
Purchase #5	$122.45	3.358%	$126.5619	$126.56	$126.55	$126.60
Purchase #6	$135.98	3.756%	$141.0874	$141.09	$141.10	$141.10
Purchase #7	$24.50	10.782%	$27.1416	$27.14	$27.15	$27.10
7 purchase totals =	$762.65		$804.0180	$804.02	$804.05	$804.00