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	$168.81	12.384%	$189.7154	$189.72	$189.70	$189.70
Purchase #2	$206.52	10.624%	$228.4607	$228.46	$228.45	$228.50
Purchase #3	$237.67	10.236%	$261.9979	$262.00	$262.00	$262.00
Purchase #4	$140.60	8.557%	$152.6311	$152.63	$152.65	$152.60
Purchase #5	$192.85	13.469%	$218.825	$218.83	$218.85	$218.80
Purchase #6	$126.56	9.459%	$138.5313	$138.53	$138.55	$138.50
Purchase #7	$90.60	10.564%	$100.171	$100.17	$100.15	$100.20
7 purchase totals =	$1,163.61		$1,290.3324	$1,290.34	$1,290.35	$1,290.30