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	$101.34	10.286%	$111.7638	$111.76	$111.75	$111.80
Purchase #2	$126.82	11.104%	$140.9021	$140.90	$140.90	$140.90
Purchase #3	$200.45	9.725%	$219.9438	$219.94	$219.95	$219.90
Purchase #4	$215.28	3.210%	$222.1905	$222.19	$222.20	$222.20
Purchase #5	$134.66	10.570%	$148.8936	$148.89	$148.90	$148.90
Purchase #6	$222.60	10.845%	$246.741	$246.74	$246.75	$246.70
Purchase #7	$150.71	9.297%	$164.7215	$164.72	$164.70	$164.70
7 purchase totals =	$1,151.86		$1,255.1563	$1,255.14	$1,255.15	$1,255.10