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	$34.98	9.862%	$38.4297	$38.43	$38.45	$38.40
Purchase #2	$16.69	3.871%	$17.3361	$17.34	$17.35	$17.30
Purchase #3	$25.78	6.610%	$27.4841	$27.48	$27.50	$27.50
Purchase #4	$18.85	5.826%	$19.9482	$19.95	$19.95	$19.90
Purchase #5	$133.59	3.216%	$137.8863	$137.89	$137.90	$137.90
Purchase #6	$97.52	11.168%	$108.411	$108.41	$108.40	$108.40
Purchase #7	$92.42	11.324%	$102.8856	$102.89	$102.90	$102.90
7 purchase totals =	$419.83		$452.3810	$452.39	$452.45	$452.30