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	$20.78	5.540%	$21.9312	$21.93	$21.95	$21.90
Purchase #2	$107.67	3.789%	$111.7496	$111.75	$111.75	$111.70
Purchase #3	$103.75	8.731%	$112.8084	$112.81	$112.80	$112.80
Purchase #4	$104.62	13.284%	$118.5177	$118.52	$118.50	$118.50
Purchase #5	$82.48	10.690%	$91.2971	$91.30	$91.30	$91.30
Purchase #6	$111.89	13.403%	$126.8866	$126.89	$126.90	$126.90
Purchase #7	$134.58	12.421%	$151.2962	$151.30	$151.30	$151.30
7 purchase totals =	$665.77		$734.4868	$734.50	$734.50	$734.40