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	$33.39	7.707%	$35.9634	$35.96	$35.95	$36.00
Purchase #2	$165.89	13.107%	$187.6332	$187.63	$187.65	$187.60
Purchase #3	$212.82	4.538%	$222.4778	$222.48	$222.50	$222.50
Purchase #4	$85.88	11.127%	$95.4359	$95.44	$95.45	$95.40
Purchase #5	$105.69	8.529%	$114.7043	$114.70	$114.70	$114.70
Purchase #6	$94.78	10.670%	$104.893	$104.89	$104.90	$104.90
Purchase #7	$120.75	3.167%	$124.5742	$124.57	$124.55	$124.60
7 purchase totals =	$819.20		$885.6818	$885.67	$885.70	$885.70