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	$209.57	3.594%	$217.1019	$217.10	$217.10	$217.10
Purchase #2	$225.99	12.737%	$254.7743	$254.77	$254.75	$254.80
Purchase #3	$217.30	13.458%	$246.5442	$246.54	$246.55	$246.50
Purchase #4	$250.37	11.601%	$279.4154	$279.42	$279.40	$279.40
Purchase #5	$9.53	11.385%	$10.615	$10.62	$10.60	$10.60
Purchase #6	$136.78	3.198%	$141.1542	$141.15	$141.15	$141.20
Purchase #7	$69.54	13.452%	$78.8945	$78.89	$78.90	$78.90
7 purchase totals =	$1,119.08		$1,228.4995	$1,228.49	$1,228.45	$1,228.50