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	$248.69	7.188%	$266.5658	$266.57	$266.55	$266.60
Purchase #2	$164.38	4.294%	$171.4385	$171.44	$171.45	$171.40
Purchase #3	$52.50	12.689%	$59.1617	$59.16	$59.15	$59.20
Purchase #4	$62.76	7.371%	$67.386	$67.39	$67.40	$67.40
Purchase #5	$57.34	13.491%	$65.0757	$65.08	$65.10	$65.10
Purchase #6	$216.25	6.678%	$230.6912	$230.69	$230.70	$230.70
Purchase #7	$108.97	3.269%	$112.5322	$112.53	$112.55	$112.50
7 purchase totals =	$910.89		$972.8511	$972.86	$972.90	$972.90