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	$224.30	13.449%	$254.4661	$254.47	$254.45	$254.50
Purchase #2	$173.56	5.140%	$182.481	$182.48	$182.50	$182.50
Purchase #3	$59.93	3.284%	$61.8981	$61.90	$61.90	$61.90
Purchase #4	$54.30	9.631%	$59.5296	$59.53	$59.55	$59.50
Purchase #5	$65.83	8.761%	$71.5974	$71.60	$71.60	$71.60
Purchase #6	$126.80	4.454%	$132.4477	$132.45	$132.45	$132.40
Purchase #7	$125.81	10.846%	$139.4554	$139.46	$139.45	$139.50
7 purchase totals =	$830.53		$901.8753	$901.89	$901.90	$901.90