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	$52.54	13.185%	$59.4674	$59.47	$59.45	$59.50
Purchase #2	$206.56	3.831%	$214.4733	$214.47	$214.45	$214.50
Purchase #3	$180.63	6.433%	$192.2499	$192.25	$192.25	$192.20
Purchase #4	$176.62	13.588%	$200.6191	$200.62	$200.60	$200.60
Purchase #5	$40.96	10.288%	$45.174	$45.17	$45.15	$45.20
Purchase #6	$136.39	10.428%	$150.6127	$150.61	$150.60	$150.60
Purchase #7	$22.34	5.677%	$23.6082	$23.61	$23.60	$23.60
7 purchase totals =	$816.04		$886.2046	$886.20	$886.10	$886.20