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	$59.58	9.107%	$65.006	$65.01	$65.00	$65.00
Purchase #2	$126.41	10.542%	$139.7361	$139.74	$139.75	$139.70
Purchase #3	$48.41	7.103%	$51.8486	$51.85	$51.85	$51.80
Purchase #4	$91.90	11.161%	$102.157	$102.16	$102.15	$102.20
Purchase #5	$8.40	7.578%	$9.0366	$9.04	$9.05	$9.00
Purchase #6	$69.32	6.593%	$73.8903	$73.89	$73.90	$73.90
Purchase #7	$198.43	13.613%	$225.4423	$225.44	$225.45	$225.40
7 purchase totals =	$602.45		$667.1169	$667.13	$667.15	$667.00