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	$102.80	3.537%	$106.436	$106.44	$106.45	$106.40
Purchase #2	$65.82	5.380%	$69.3611	$69.36	$69.35	$69.40
Purchase #3	$71.42	13.426%	$81.0088	$81.01	$81.00	$81.00
Purchase #4	$168.85	12.392%	$189.7739	$189.77	$189.75	$189.80
Purchase #5	$66.34	10.699%	$73.4377	$73.44	$73.45	$73.40
Purchase #6	$85.92	4.265%	$89.5845	$89.58	$89.60	$89.60
Purchase #7	$139.79	9.145%	$152.5738	$152.57	$152.55	$152.60
7 purchase totals =	$700.94		$762.1758	$762.17	$762.15	$762.20