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	$213.25	12.634%	$240.192	$240.19	$240.20	$240.20
Purchase #2	$105.96	7.447%	$113.8508	$113.85	$113.85	$113.90
Purchase #3	$79.54	5.464%	$83.8861	$83.89	$83.90	$83.90
Purchase #4	$97.26	5.759%	$102.8612	$102.86	$102.85	$102.90
Purchase #5	$39.73	9.473%	$43.4936	$43.49	$43.50	$43.50
Purchase #6	$52.72	12.385%	$59.2494	$59.25	$59.25	$59.20
Purchase #7	$73.55	4.282%	$76.6994	$76.70	$76.70	$76.70
7 purchase totals =	$662.01		$720.2325	$720.23	$720.25	$720.30