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	$225.61	6.449%	$240.1596	$240.16	$240.15	$240.20
Purchase #2	$210.82	13.133%	$238.507	$238.51	$238.50	$238.50
Purchase #3	$225.91	13.690%	$256.8371	$256.84	$256.85	$256.80
Purchase #4	$29.60	6.785%	$31.6084	$31.61	$31.60	$31.60
Purchase #5	$76.32	11.461%	$85.067	$85.07	$85.05	$85.10
Purchase #6	$221.71	9.587%	$242.9653	$242.97	$242.95	$243.00
Purchase #7	$7.46	9.273%	$8.1518	$8.15	$8.15	$8.20
7 purchase totals =	$997.43		$1,103.2962	$1,103.31	$1,103.25	$1,103.40