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	$158.39	8.549%	$171.9308	$171.93	$171.95	$171.90
Purchase #2	$215.88	4.504%	$225.6032	$225.60	$225.60	$225.60
Purchase #3	$143.67	11.165%	$159.7108	$159.71	$159.70	$159.70
Purchase #4	$97.34	7.447%	$104.5889	$104.59	$104.60	$104.60
Purchase #5	$63.65	5.561%	$67.1896	$67.19	$67.20	$67.20
Purchase #6	$217.28	11.541%	$242.3563	$242.36	$242.35	$242.40
Purchase #7	$38.61	12.548%	$43.4548	$43.45	$43.45	$43.50
7 purchase totals =	$934.82		$1,014.8344	$1,014.83	$1,014.85	$1,014.90