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	$217.28	4.476%	$227.0055	$227.01	$227.00	$227.00
Purchase #2	$38.59	5.430%	$40.6854	$40.69	$40.70	$40.70
Purchase #3	$9.89	10.361%	$10.9147	$10.91	$10.90	$10.90
Purchase #4	$169.69	6.210%	$180.2277	$180.23	$180.25	$180.20
Purchase #5	$141.91	10.125%	$156.2784	$156.28	$156.30	$156.30
Purchase #6	$117.61	8.759%	$127.9115	$127.91	$127.90	$127.90
Purchase #7	$183.99	13.240%	$208.3503	$208.35	$208.35	$208.40
7 purchase totals =	$878.96		$951.3735	$951.38	$951.40	$951.40