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	$64.60	12.317%	$72.5568	$72.56	$72.55	$72.60
Purchase #2	$211.59	5.266%	$222.7323	$222.73	$222.75	$222.70
Purchase #3	$239.71	5.732%	$253.4502	$253.45	$253.45	$253.50
Purchase #4	$17.25	4.445%	$18.0168	$18.02	$18.00	$18.00
Purchase #5	$84.79	12.643%	$95.51	$95.51	$95.50	$95.50
Purchase #6	$166.55	11.463%	$185.6416	$185.64	$185.65	$185.60
Purchase #7	$137.32	6.246%	$145.897	$145.90	$145.90	$145.90
7 purchase totals =	$921.81		$993.8047	$993.81	$993.80	$993.80