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	$166.63	12.667%	$187.737	$187.74	$187.75	$187.70
Purchase #2	$145.75	5.484%	$153.7429	$153.74	$153.75	$153.70
Purchase #3	$137.28	11.797%	$153.4749	$153.47	$153.45	$153.50
Purchase #4	$139.93	8.463%	$151.7723	$151.77	$151.75	$151.80
Purchase #5	$134.66	7.513%	$144.777	$144.78	$144.80	$144.80
Purchase #6	$55.85	10.618%	$61.7802	$61.78	$61.80	$61.80
Purchase #7	$159.57	11.858%	$178.4918	$178.49	$178.50	$178.50
7 purchase totals =	$939.67		$1,031.7761	$1,031.77	$1,031.80	$1,031.80