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	$214.61	7.115%	$229.8795	$229.88	$229.90	$229.90
Purchase #2	$15.52	6.258%	$16.4912	$16.49	$16.50	$16.50
Purchase #3	$109.54	12.315%	$123.0299	$123.03	$123.05	$123.00
Purchase #4	$189.90	11.676%	$212.0727	$212.07	$212.05	$212.10
Purchase #5	$35.53	13.182%	$40.2136	$40.21	$40.20	$40.20
Purchase #6	$158.49	8.589%	$172.1027	$172.10	$172.10	$172.10
Purchase #7	$40.83	11.324%	$45.4536	$45.45	$45.45	$45.50
7 purchase totals =	$764.42		$839.2432	$839.23	$839.25	$839.30