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	$24.92	3.669%	$25.8343	$25.83	$25.85	$25.80
Purchase #2	$158.95	6.710%	$169.6155	$169.62	$169.60	$169.60
Purchase #3	$210.50	13.165%	$238.2123	$238.21	$238.20	$238.20
Purchase #4	$23.66	3.624%	$24.5174	$24.52	$24.50	$24.50
Purchase #5	$59.46	6.719%	$63.4551	$63.46	$63.45	$63.50
Purchase #6	$32.48	3.253%	$33.5366	$33.54	$33.55	$33.50
Purchase #7	$59.59	11.548%	$66.4715	$66.47	$66.45	$66.50
7 purchase totals =	$569.56		$621.6427	$621.65	$621.60	$621.60