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	$132.63	11.168%	$147.4421	$147.44	$147.45	$147.40
Purchase #2	$158.58	3.723%	$164.4839	$164.48	$164.50	$164.50
Purchase #3	$27.66	3.388%	$28.5971	$28.60	$28.60	$28.60
Purchase #4	$133.49	7.313%	$143.2521	$143.25	$143.25	$143.30
Purchase #5	$212.30	3.204%	$219.1021	$219.10	$219.10	$219.10
Purchase #6	$125.70	5.685%	$132.846	$132.85	$132.85	$132.80
Purchase #7	$61.86	6.858%	$66.1024	$66.10	$66.10	$66.10
7 purchase totals =	$852.22		$901.8257	$901.82	$901.85	$901.80