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	$235.99	6.198%	$250.6167	$250.62	$250.60	$250.60
Purchase #2	$106.32	6.210%	$112.9225	$112.92	$112.90	$112.90
Purchase #3	$205.40	8.378%	$222.6084	$222.61	$222.60	$222.60
Purchase #4	$244.49	6.593%	$260.6092	$260.61	$260.60	$260.60
Purchase #5	$31.99	9.475%	$35.0211	$35.02	$35.00	$35.00
Purchase #6	$143.43	8.381%	$155.4509	$155.45	$155.45	$155.50
Purchase #7	$126.67	3.582%	$131.2073	$131.21	$131.20	$131.20
7 purchase totals =	$1,094.29		$1,168.4361	$1,168.44	$1,168.35	$1,168.40