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	$128.36	10.586%	$141.9482	$141.95	$141.95	$141.90
Purchase #2	$123.96	6.153%	$131.5873	$131.59	$131.60	$131.60
Purchase #3	$116.25	9.576%	$127.3821	$127.38	$127.40	$127.40
Purchase #4	$236.47	8.472%	$256.5037	$256.50	$256.50	$256.50
Purchase #5	$227.89	10.289%	$251.3376	$251.34	$251.35	$251.30
Purchase #6	$216.27	10.270%	$238.4809	$238.48	$238.50	$238.50
Purchase #7	$184.32	13.139%	$208.5378	$208.54	$208.55	$208.50
7 purchase totals =	$1,233.52		$1,355.7776	$1,355.78	$1,355.85	$1,355.70