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	$22.42	8.143%	$24.2457	$24.25	$24.25	$24.20
Purchase #2	$78.89	3.443%	$81.6062	$81.61	$81.60	$81.60
Purchase #3	$72.29	5.105%	$75.9804	$75.98	$76.00	$76.00
Purchase #4	$103.37	6.271%	$109.8523	$109.85	$109.85	$109.90
Purchase #5	$66.57	6.314%	$70.7732	$70.77	$70.75	$70.80
Purchase #6	$77.61	11.236%	$86.3303	$86.33	$86.35	$86.30
Purchase #7	$73.77	8.740%	$80.2175	$80.22	$80.20	$80.20
7 purchase totals =	$494.92		$529.0056	$529.01	$529.00	$529.00