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	$127.26	7.132%	$136.3362	$136.34	$136.35	$136.30
Purchase #2	$19.82	3.719%	$20.5571	$20.56	$20.55	$20.60
Purchase #3	$40.71	5.544%	$42.967	$42.97	$42.95	$43.00
Purchase #4	$90.37	12.752%	$101.894	$101.89	$101.90	$101.90
Purchase #5	$133.30	4.462%	$139.2478	$139.25	$139.25	$139.20
Purchase #6	$192.79	8.680%	$209.5242	$209.52	$209.50	$209.50
Purchase #7	$105.59	11.658%	$117.8997	$117.90	$117.90	$117.90
7 purchase totals =	$709.84		$768.4260	$768.43	$768.40	$768.40