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	$112.78	13.259%	$127.7335	$127.73	$127.75	$127.70
Purchase #2	$33.82	10.610%	$37.4083	$37.41	$37.40	$37.40
Purchase #3	$27.61	11.177%	$30.696	$30.70	$30.70	$30.70
Purchase #4	$247.85	7.471%	$266.3669	$266.37	$266.35	$266.40
Purchase #5	$51.57	11.269%	$57.3814	$57.38	$57.40	$57.40
Purchase #6	$87.61	5.231%	$92.1929	$92.19	$92.20	$92.20
Purchase #7	$242.95	5.706%	$256.8127	$256.81	$256.80	$256.80
7 purchase totals =	$804.19		$868.5917	$868.59	$868.60	$868.60