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	$41.26	4.855%	$43.2632	$43.26	$43.25	$43.30
Purchase #2	$186.72	6.461%	$198.784	$198.78	$198.80	$198.80
Purchase #3	$139.95	9.692%	$153.514	$153.51	$153.50	$153.50
Purchase #4	$150.71	13.654%	$171.2879	$171.29	$171.30	$171.30
Purchase #5	$116.68	10.500%	$128.9314	$128.93	$128.95	$128.90
Purchase #6	$160.38	4.770%	$168.0301	$168.03	$168.05	$168.00
Purchase #7	$84.35	9.619%	$92.4636	$92.46	$92.45	$92.50
7 purchase totals =	$880.05		$956.2742	$956.26	$956.30	$956.30