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	$40.65	12.321%	$45.6585	$45.66	$45.65	$45.70
Purchase #2	$31.79	11.247%	$35.3654	$35.37	$35.35	$35.40
Purchase #3	$125.63	5.146%	$132.0949	$132.09	$132.10	$132.10
Purchase #4	$162.71	3.797%	$168.8881	$168.89	$168.90	$168.90
Purchase #5	$239.38	13.462%	$271.6053	$271.61	$271.60	$271.60
Purchase #6	$165.98	8.148%	$179.5041	$179.50	$179.50	$179.50
Purchase #7	$106.38	9.712%	$116.7116	$116.71	$116.70	$116.70
7 purchase totals =	$872.52		$949.8279	$949.83	$949.80	$949.90