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	$151.71	12.639%	$170.8846	$170.88	$170.90	$170.90
Purchase #2	$144.42	9.748%	$158.4981	$158.50	$158.50	$158.50
Purchase #3	$131.90	3.874%	$137.0098	$137.01	$137.00	$137.00
Purchase #4	$80.95	10.634%	$89.5582	$89.56	$89.55	$89.60
Purchase #5	$42.66	4.148%	$44.4295	$44.43	$44.45	$44.40
Purchase #6	$19.55	13.797%	$22.2473	$22.25	$22.25	$22.20
Purchase #7	$169.43	4.334%	$176.7731	$176.77	$176.75	$176.80
7 purchase totals =	$740.62		$799.4006	$799.40	$799.40	$799.40