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	$130.39	11.823%	$145.806	$145.81	$145.80	$145.80
Purchase #2	$162.86	3.165%	$168.0145	$168.01	$168.00	$168.00
Purchase #3	$180.47	10.728%	$199.8308	$199.83	$199.85	$199.80
Purchase #4	$151.92	4.102%	$158.1518	$158.15	$158.15	$158.20
Purchase #5	$6.60	8.293%	$7.1473	$7.15	$7.15	$7.10
Purchase #6	$65.27	10.387%	$72.0496	$72.05	$72.05	$72.00
Purchase #7	$138.38	9.854%	$152.016	$152.02	$152.00	$152.00
7 purchase totals =	$835.89		$903.0160	$903.02	$903.00	$902.90