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	$206.62	10.557%	$228.4329	$228.43	$228.45	$228.40
Purchase #2	$199.40	8.659%	$216.666	$216.67	$216.65	$216.70
Purchase #3	$208.33	10.164%	$229.5047	$229.50	$229.50	$229.50
Purchase #4	$35.68	12.790%	$40.2435	$40.24	$40.25	$40.20
Purchase #5	$196.29	5.180%	$206.4578	$206.46	$206.45	$206.50
Purchase #6	$101.80	9.520%	$111.4914	$111.49	$111.50	$111.50
Purchase #7	$229.52	11.239%	$255.3158	$255.32	$255.30	$255.30
7 purchase totals =	$1,177.64		$1,288.1121	$1,288.11	$1,288.10	$1,288.10