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	$134.43	13.523%	$152.609	$152.61	$152.60	$152.60
Purchase #2	$66.72	10.249%	$73.5581	$73.56	$73.55	$73.60
Purchase #3	$238.86	12.828%	$269.501	$269.50	$269.50	$269.50
Purchase #4	$18.55	4.186%	$19.3265	$19.33	$19.35	$19.30
Purchase #5	$9.39	12.748%	$10.587	$10.59	$10.60	$10.60
Purchase #6	$161.57	4.685%	$169.1396	$169.14	$169.15	$169.10
Purchase #7	$241.97	5.617%	$255.5615	$255.56	$255.55	$255.60
7 purchase totals =	$871.49		$950.2827	$950.29	$950.30	$950.30