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	$216.82	10.184%	$238.9009	$238.90	$238.90	$238.90
Purchase #2	$150.83	6.464%	$160.5797	$160.58	$160.60	$160.60
Purchase #3	$54.99	12.342%	$61.7769	$61.78	$61.80	$61.80
Purchase #4	$151.38	3.423%	$156.5617	$156.56	$156.55	$156.60
Purchase #5	$79.43	13.268%	$89.9688	$89.97	$89.95	$90.00
Purchase #6	$45.61	4.128%	$47.4928	$47.49	$47.50	$47.50
Purchase #7	$193.85	7.509%	$208.4062	$208.41	$208.40	$208.40
7 purchase totals =	$892.91		$963.6870	$963.69	$963.70	$963.80