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	$93.29	12.472%	$104.9251	$104.93	$104.95	$104.90
Purchase #2	$167.53	10.468%	$185.067	$185.07	$185.05	$185.10
Purchase #3	$77.25	6.165%	$82.0125	$82.01	$82.00	$82.00
Purchase #4	$124.97	6.107%	$132.6019	$132.60	$132.60	$132.60
Purchase #5	$95.38	9.770%	$104.6986	$104.70	$104.70	$104.70
Purchase #6	$143.52	12.280%	$161.1443	$161.14	$161.15	$161.10
Purchase #7	$73.55	12.120%	$82.4643	$82.46	$82.45	$82.50
7 purchase totals =	$775.49		$852.9137	$852.91	$852.90	$852.90