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	$51.81	6.170%	$55.0067	$55.01	$55.00	$55.00
Purchase #2	$52.53	4.845%	$55.0751	$55.08	$55.10	$55.10
Purchase #3	$119.75	13.675%	$136.1258	$136.13	$136.15	$136.10
Purchase #4	$29.59	6.563%	$31.532	$31.53	$31.55	$31.50
Purchase #5	$248.58	10.619%	$274.9767	$274.98	$275.00	$275.00
Purchase #6	$111.41	11.222%	$123.9124	$123.91	$123.90	$123.90
Purchase #7	$175.32	13.447%	$198.8953	$198.90	$198.90	$198.90
7 purchase totals =	$788.99		$875.5240	$875.54	$875.60	$875.50