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	$149.62	13.496%	$169.8127	$169.81	$169.80	$169.80
Purchase #2	$187.34	11.586%	$209.0452	$209.05	$209.05	$209.00
Purchase #3	$140.94	6.672%	$150.3435	$150.34	$150.35	$150.30
Purchase #4	$218.93	8.146%	$236.764	$236.76	$236.75	$236.80
Purchase #5	$95.60	5.293%	$100.6601	$100.66	$100.65	$100.70
Purchase #6	$170.74	10.471%	$188.6182	$188.62	$188.60	$188.60
Purchase #7	$29.85	5.871%	$31.6025	$31.60	$31.60	$31.60
7 purchase totals =	$993.02		$1,086.8462	$1,086.84	$1,086.80	$1,086.80