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	$188.71	9.391%	$206.4318	$206.43	$206.45	$206.40
Purchase #2	$36.32	8.814%	$39.5212	$39.52	$39.50	$39.50
Purchase #3	$68.86	5.288%	$72.5013	$72.50	$72.50	$72.50
Purchase #4	$45.36	4.509%	$47.4053	$47.41	$47.40	$47.40
Purchase #5	$23.69	6.126%	$25.1412	$25.14	$25.15	$25.10
Purchase #6	$200.54	11.125%	$222.8501	$222.85	$222.85	$222.90
Purchase #7	$117.69	6.626%	$125.4881	$125.49	$125.50	$125.50
7 purchase totals =	$681.17		$739.3390	$739.34	$739.35	$739.30