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	$219.32	8.836%	$238.6991	$238.70	$238.70	$238.70
Purchase #2	$219.71	3.601%	$227.6218	$227.62	$227.60	$227.60
Purchase #3	$99.41	12.557%	$111.8929	$111.89	$111.90	$111.90
Purchase #4	$164.93	4.798%	$172.8433	$172.84	$172.85	$172.80
Purchase #5	$105.60	8.715%	$114.803	$114.80	$114.80	$114.80
Purchase #6	$229.43	6.648%	$244.6825	$244.68	$244.70	$244.70
Purchase #7	$36.53	12.259%	$41.0082	$41.01	$41.00	$41.00
7 purchase totals =	$1,074.93		$1,151.5508	$1,151.54	$1,151.55	$1,151.50