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	$103.58	13.827%	$117.902	$117.90	$117.90	$117.90
Purchase #2	$40.94	3.799%	$42.4953	$42.50	$42.50	$42.50
Purchase #3	$161.39	12.405%	$181.4104	$181.41	$181.40	$181.40
Purchase #4	$81.95	4.182%	$85.3771	$85.38	$85.40	$85.40
Purchase #5	$220.61	10.167%	$243.0394	$243.04	$243.05	$243.00
Purchase #6	$204.50	3.706%	$212.0788	$212.08	$212.10	$212.10
Purchase #7	$43.81	5.854%	$46.3746	$46.37	$46.35	$46.40
7 purchase totals =	$856.78		$928.6776	$928.68	$928.70	$928.70