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	$32.47	7.243%	$34.8218	$34.82	$34.80	$34.80
Purchase #2	$145.62	9.531%	$159.499	$159.50	$159.50	$159.50
Purchase #3	$230.27	5.496%	$242.9256	$242.93	$242.95	$242.90
Purchase #4	$104.71	9.301%	$114.4491	$114.45	$114.45	$114.40
Purchase #5	$154.35	9.862%	$169.572	$169.57	$169.55	$169.60
Purchase #6	$246.56	9.291%	$269.4679	$269.47	$269.45	$269.50
Purchase #7	$132.39	3.188%	$136.6106	$136.61	$136.60	$136.60
7 purchase totals =	$1,046.37		$1,127.3460	$1,127.35	$1,127.30	$1,127.30