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	$196.84	10.124%	$216.7681	$216.77	$216.75	$216.80
Purchase #2	$64.74	9.861%	$71.124	$71.12	$71.10	$71.10
Purchase #3	$66.74	11.585%	$74.4718	$74.47	$74.45	$74.50
Purchase #4	$31.86	11.538%	$35.536	$35.54	$35.55	$35.50
Purchase #5	$60.86	9.863%	$66.8626	$66.86	$66.85	$66.90
Purchase #6	$52.78	8.456%	$57.2431	$57.24	$57.25	$57.20
Purchase #7	$46.95	6.215%	$49.8679	$49.87	$49.85	$49.90
7 purchase totals =	$520.77		$571.8735	$571.87	$571.80	$571.90