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	$194.54	13.819%	$221.4235	$221.42	$221.40	$221.40
Purchase #2	$192.56	8.140%	$208.2344	$208.23	$208.25	$208.20
Purchase #3	$101.42	10.182%	$111.7466	$111.75	$111.75	$111.70
Purchase #4	$182.43	11.412%	$203.2489	$203.25	$203.25	$203.20
Purchase #5	$189.85	4.585%	$198.5546	$198.55	$198.55	$198.60
Purchase #6	$190.78	12.579%	$214.7782	$214.78	$214.80	$214.80
Purchase #7	$242.80	11.808%	$271.4698	$271.47	$271.45	$271.50
7 purchase totals =	$1,294.38		$1,429.4560	$1,429.45	$1,429.45	$1,429.40