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	$208.69	4.812%	$218.7322	$218.73	$218.75	$218.70
Purchase #2	$101.71	10.565%	$112.4557	$112.46	$112.45	$112.50
Purchase #3	$199.45	11.722%	$222.8295	$222.83	$222.85	$222.80
Purchase #4	$56.66	3.184%	$58.4641	$58.46	$58.45	$58.50
Purchase #5	$87.87	11.727%	$98.1745	$98.17	$98.15	$98.20
Purchase #6	$17.97	10.281%	$19.8175	$19.82	$19.80	$19.80
Purchase #7	$33.80	13.811%	$38.4681	$38.47	$38.45	$38.50
7 purchase totals =	$706.15		$768.9416	$768.94	$768.90	$769.00