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	$215.91	11.854%	$241.504	$241.50	$241.50	$241.50
Purchase #2	$90.58	9.380%	$99.0764	$99.08	$99.10	$99.10
Purchase #3	$36.58	13.332%	$41.4568	$41.46	$41.45	$41.50
Purchase #4	$121.64	11.863%	$136.0702	$136.07	$136.05	$136.10
Purchase #5	$219.85	9.129%	$239.9201	$239.92	$239.90	$239.90
Purchase #6	$242.75	6.788%	$259.2279	$259.23	$259.25	$259.20
Purchase #7	$40.67	9.396%	$44.4914	$44.49	$44.50	$44.50
7 purchase totals =	$967.98		$1,061.7468	$1,061.75	$1,061.75	$1,061.80