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	$232.69	11.346%	$259.091	$259.09	$259.10	$259.10
Purchase #2	$210.91	6.754%	$225.1549	$225.15	$225.15	$225.20
Purchase #3	$102.53	8.381%	$111.123	$111.12	$111.10	$111.10
Purchase #4	$181.45	10.717%	$200.896	$200.90	$200.90	$200.90
Purchase #5	$41.52	4.874%	$43.5437	$43.54	$43.55	$43.50
Purchase #6	$28.82	11.674%	$32.1844	$32.18	$32.20	$32.20
Purchase #7	$40.69	10.601%	$45.0035	$45.00	$45.00	$45.00
7 purchase totals =	$838.61		$916.9965	$916.98	$917.00	$917.00