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	$100.47	5.175%	$105.6693	$105.67	$105.65	$105.70
Purchase #2	$41.73	8.851%	$45.4235	$45.42	$45.40	$45.40
Purchase #3	$125.56	10.871%	$139.2096	$139.21	$139.20	$139.20
Purchase #4	$56.64	9.154%	$61.8248	$61.82	$61.80	$61.80
Purchase #5	$148.81	4.472%	$155.4648	$155.46	$155.45	$155.50
Purchase #6	$239.66	8.172%	$259.245	$259.25	$259.25	$259.20
Purchase #7	$164.34	12.799%	$185.3739	$185.37	$185.35	$185.40
7 purchase totals =	$877.21		$952.2109	$952.20	$952.10	$952.20