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	$228.32	10.344%	$251.9374	$251.94	$251.95	$251.90
Purchase #2	$33.54	4.295%	$34.9805	$34.98	$35.00	$35.00
Purchase #3	$182.74	4.300%	$190.5978	$190.60	$190.60	$190.60
Purchase #4	$61.72	5.138%	$64.8912	$64.89	$64.90	$64.90
Purchase #5	$18.90	11.691%	$21.1096	$21.11	$21.10	$21.10
Purchase #6	$94.31	9.133%	$102.9233	$102.92	$102.90	$102.90
Purchase #7	$65.85	11.763%	$73.5959	$73.60	$73.60	$73.60
7 purchase totals =	$685.38		$740.0357	$740.04	$740.05	$740.00