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	$55.85	5.341%	$58.8329	$58.83	$58.85	$58.80
Purchase #2	$224.26	8.323%	$242.9252	$242.93	$242.95	$242.90
Purchase #3	$110.49	11.674%	$123.3886	$123.39	$123.40	$123.40
Purchase #4	$238.52	7.554%	$256.5378	$256.54	$256.55	$256.50
Purchase #5	$81.78	11.300%	$91.0211	$91.02	$91.00	$91.00
Purchase #6	$57.43	12.338%	$64.5157	$64.52	$64.50	$64.50
Purchase #7	$54.76	8.778%	$59.5668	$59.57	$59.55	$59.60
7 purchase totals =	$823.09		$896.7881	$896.80	$896.80	$896.70