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	$102.42	9.601%	$112.2533	$112.25	$112.25	$112.30
Purchase #2	$199.53	5.655%	$210.8134	$210.81	$210.80	$210.80
Purchase #3	$49.56	5.277%	$52.1753	$52.18	$52.20	$52.20
Purchase #4	$232.49	8.396%	$252.0099	$252.01	$252.00	$252.00
Purchase #5	$29.85	6.828%	$31.8882	$31.89	$31.90	$31.90
Purchase #6	$42.41	7.199%	$45.4631	$45.46	$45.45	$45.50
Purchase #7	$59.37	4.329%	$61.9401	$61.94	$61.95	$61.90
7 purchase totals =	$715.63		$766.5433	$766.54	$766.55	$766.60