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	$86.77	3.660%	$89.9458	$89.95	$89.95	$89.90
Purchase #2	$7.93	8.603%	$8.6122	$8.61	$8.60	$8.60
Purchase #3	$222.52	6.582%	$237.1663	$237.17	$237.15	$237.20
Purchase #4	$201.43	3.742%	$208.9675	$208.97	$208.95	$209.00
Purchase #5	$69.39	5.117%	$72.9407	$72.94	$72.95	$72.90
Purchase #6	$7.49	13.228%	$8.4808	$8.48	$8.50	$8.50
Purchase #7	$79.68	12.664%	$89.7707	$89.77	$89.75	$89.80
7 purchase totals =	$675.21		$715.8840	$715.89	$715.85	$715.90