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	$192.93	3.464%	$199.6131	$199.61	$199.60	$199.60
Purchase #2	$138.94	6.769%	$148.3448	$148.34	$148.35	$148.30
Purchase #3	$189.86	13.535%	$215.5576	$215.56	$215.55	$215.60
Purchase #4	$155.33	5.617%	$164.0549	$164.05	$164.05	$164.10
Purchase #5	$22.35	8.290%	$24.2028	$24.20	$24.20	$24.20
Purchase #6	$82.27	9.639%	$90.2	$90.20	$90.20	$90.20
Purchase #7	$177.67	6.707%	$189.5863	$189.59	$189.60	$189.60
7 purchase totals =	$959.35		$1,031.5595	$1,031.55	$1,031.55	$1,031.60