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	$87.49	6.183%	$92.8995	$92.90	$92.90	$92.90
Purchase #2	$83.53	4.789%	$87.5303	$87.53	$87.55	$87.50
Purchase #3	$17.42	5.742%	$18.4203	$18.42	$18.40	$18.40
Purchase #4	$126.78	8.714%	$137.8276	$137.83	$137.85	$137.80
Purchase #5	$40.58	6.512%	$43.2226	$43.22	$43.20	$43.20
Purchase #6	$204.73	5.729%	$216.459	$216.46	$216.45	$216.50
Purchase #7	$155.90	7.859%	$168.1522	$168.15	$168.15	$168.20
7 purchase totals =	$716.43		$764.5115	$764.51	$764.50	$764.50