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	$118.86	11.334%	$132.3316	$132.33	$132.35	$132.30
Purchase #2	$129.88	5.133%	$136.5467	$136.55	$136.55	$136.50
Purchase #3	$236.99	10.196%	$261.1535	$261.15	$261.15	$261.20
Purchase #4	$40.62	7.175%	$43.5345	$43.53	$43.55	$43.50
Purchase #5	$70.37	3.189%	$72.6141	$72.61	$72.60	$72.60
Purchase #6	$92.82	5.117%	$97.5696	$97.57	$97.55	$97.60
Purchase #7	$124.83	9.501%	$136.6901	$136.69	$136.70	$136.70
7 purchase totals =	$814.37		$880.4401	$880.43	$880.45	$880.40