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	$126.37	12.170%	$141.7492	$141.75	$141.75	$141.70
Purchase #2	$205.44	10.594%	$227.2043	$227.20	$227.20	$227.20
Purchase #3	$228.29	11.866%	$255.3789	$255.38	$255.40	$255.40
Purchase #4	$214.49	6.584%	$228.612	$228.61	$228.60	$228.60
Purchase #5	$38.73	4.346%	$40.4132	$40.41	$40.40	$40.40
Purchase #6	$113.40	5.380%	$119.5009	$119.50	$119.50	$119.50
Purchase #7	$77.40	7.114%	$82.9062	$82.91	$82.90	$82.90
7 purchase totals =	$1,004.12		$1,095.7647	$1,095.76	$1,095.75	$1,095.70