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	$183.33	3.830%	$190.3515	$190.35	$190.35	$190.40
Purchase #2	$146.92	12.338%	$165.047	$165.05	$165.05	$165.00
Purchase #3	$34.30	10.548%	$37.918	$37.92	$37.90	$37.90
Purchase #4	$38.94	9.260%	$42.5458	$42.55	$42.55	$42.50
Purchase #5	$210.54	10.118%	$231.8424	$231.84	$231.85	$231.80
Purchase #6	$7.52	3.275%	$7.7663	$7.77	$7.75	$7.80
Purchase #7	$182.77	9.324%	$199.8115	$199.81	$199.80	$199.80
7 purchase totals =	$804.32		$875.2825	$875.29	$875.25	$875.20