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	$103.25	7.827%	$111.3314	$111.33	$111.35	$111.30
Purchase #2	$126.25	9.641%	$138.4218	$138.42	$138.40	$138.40
Purchase #3	$222.83	13.652%	$253.2508	$253.25	$253.25	$253.30
Purchase #4	$31.65	11.847%	$35.3996	$35.40	$35.40	$35.40
Purchase #5	$230.56	11.408%	$256.8623	$256.86	$256.85	$256.90
Purchase #6	$205.88	5.156%	$216.4952	$216.50	$216.50	$216.50
Purchase #7	$227.74	5.223%	$239.6349	$239.63	$239.65	$239.60
7 purchase totals =	$1,148.16		$1,251.3960	$1,251.39	$1,251.40	$1,251.40