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	$126.93	4.252%	$132.3271	$132.33	$132.35	$132.30
Purchase #2	$101.42	11.510%	$113.0934	$113.09	$113.10	$113.10
Purchase #3	$48.89	10.211%	$53.8822	$53.88	$53.90	$53.90
Purchase #4	$74.36	12.421%	$83.5963	$83.60	$83.60	$83.60
Purchase #5	$213.81	12.479%	$240.4913	$240.49	$240.50	$240.50
Purchase #6	$153.70	6.785%	$164.1285	$164.13	$164.15	$164.10
Purchase #7	$136.78	13.453%	$155.181	$155.18	$155.20	$155.20
7 purchase totals =	$855.89		$942.6998	$942.70	$942.80	$942.70