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	$226.38	13.285%	$256.4546	$256.45	$256.45	$256.50
Purchase #2	$73.92	6.232%	$78.5267	$78.53	$78.55	$78.50
Purchase #3	$212.29	10.661%	$234.9222	$234.92	$234.90	$234.90
Purchase #4	$77.67	4.131%	$80.8785	$80.88	$80.90	$80.90
Purchase #5	$94.29	5.632%	$99.6004	$99.60	$99.60	$99.60
Purchase #6	$78.85	11.638%	$88.0266	$88.03	$88.05	$88.00
Purchase #7	$170.77	12.569%	$192.2341	$192.23	$192.25	$192.20
7 purchase totals =	$934.17		$1,030.6431	$1,030.64	$1,030.70	$1,030.60