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	$100.28	4.865%	$105.1586	$105.16	$105.15	$105.20
Purchase #2	$112.40	5.290%	$118.346	$118.35	$118.35	$118.30
Purchase #3	$122.42	7.291%	$131.3456	$131.35	$131.35	$131.30
Purchase #4	$172.84	8.477%	$187.4916	$187.49	$187.50	$187.50
Purchase #5	$90.72	11.269%	$100.9432	$100.94	$100.95	$100.90
Purchase #6	$180.49	6.759%	$192.6893	$192.69	$192.70	$192.70
Purchase #7	$12.26	3.660%	$12.7087	$12.71	$12.70	$12.70
7 purchase totals =	$791.41		$848.6830	$848.69	$848.70	$848.60