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	$100.58	4.508%	$105.1141	$105.11	$105.10	$105.10
Purchase #2	$164.96	3.148%	$170.1529	$170.15	$170.15	$170.20
Purchase #3	$21.58	13.325%	$24.4555	$24.46	$24.45	$24.50
Purchase #4	$145.45	7.202%	$155.9253	$155.93	$155.95	$155.90
Purchase #5	$77.78	13.449%	$88.2406	$88.24	$88.25	$88.20
Purchase #6	$91.47	4.503%	$95.5889	$95.59	$95.60	$95.60
Purchase #7	$147.54	3.667%	$152.9503	$152.95	$152.95	$153.00
7 purchase totals =	$749.36		$792.4276	$792.43	$792.45	$792.50