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	$126.58	7.661%	$136.2773	$136.28	$136.30	$136.30
Purchase #2	$221.88	9.258%	$242.4217	$242.42	$242.40	$242.40
Purchase #3	$113.59	4.641%	$118.8617	$118.86	$118.85	$118.90
Purchase #4	$246.62	6.426%	$262.4678	$262.47	$262.45	$262.50
Purchase #5	$165.73	6.518%	$176.5323	$176.53	$176.55	$176.50
Purchase #6	$80.57	9.695%	$88.3813	$88.38	$88.40	$88.40
Purchase #7	$177.51	13.156%	$200.8632	$200.86	$200.85	$200.90
7 purchase totals =	$1,132.48		$1,225.8053	$1,225.80	$1,225.80	$1,225.90