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	$191.74	13.165%	$216.9826	$216.98	$217.00	$217.00
Purchase #2	$50.79	11.149%	$56.4526	$56.45	$56.45	$56.50
Purchase #3	$99.77	12.807%	$112.5475	$112.55	$112.55	$112.50
Purchase #4	$66.28	10.103%	$72.9763	$72.98	$73.00	$73.00
Purchase #5	$87.61	10.112%	$96.4691	$96.47	$96.45	$96.50
Purchase #6	$112.74	4.515%	$117.8302	$117.83	$117.85	$117.80
Purchase #7	$100.70	12.835%	$113.6248	$113.62	$113.60	$113.60
7 purchase totals =	$709.63		$786.8831	$786.88	$786.90	$786.90