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	$141.29	11.556%	$157.6175	$157.62	$157.60	$157.60
Purchase #2	$32.89	8.117%	$35.5597	$35.56	$35.55	$35.60
Purchase #3	$166.42	8.517%	$180.594	$180.59	$180.60	$180.60
Purchase #4	$45.55	9.642%	$49.9419	$49.94	$49.95	$49.90
Purchase #5	$108.65	5.378%	$114.4932	$114.49	$114.50	$114.50
Purchase #6	$66.48	9.663%	$72.904	$72.90	$72.90	$72.90
Purchase #7	$120.69	8.644%	$131.1224	$131.12	$131.10	$131.10
7 purchase totals =	$681.97		$742.2327	$742.22	$742.20	$742.20