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	$201.67	10.319%	$222.4803	$222.48	$222.50	$222.50
Purchase #2	$52.34	12.602%	$58.9359	$58.94	$58.95	$58.90
Purchase #3	$180.78	5.194%	$190.1697	$190.17	$190.15	$190.20
Purchase #4	$61.26	8.460%	$66.4426	$66.44	$66.45	$66.40
Purchase #5	$38.84	10.476%	$42.9089	$42.91	$42.90	$42.90
Purchase #6	$51.57	13.421%	$58.4912	$58.49	$58.50	$58.50
Purchase #7	$69.56	11.576%	$77.6123	$77.61	$77.60	$77.60
7 purchase totals =	$656.02		$717.0409	$717.04	$717.05	$717.00