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	$81.64	7.215%	$87.5303	$87.53	$87.55	$87.50
Purchase #2	$12.29	5.245%	$12.9346	$12.93	$12.95	$12.90
Purchase #3	$111.35	11.598%	$124.2644	$124.26	$124.25	$124.30
Purchase #4	$66.79	8.379%	$72.3863	$72.39	$72.40	$72.40
Purchase #5	$132.52	7.867%	$142.9453	$142.95	$142.95	$142.90
Purchase #6	$75.76	3.423%	$78.3533	$78.35	$78.35	$78.40
Purchase #7	$167.72	8.368%	$181.7548	$181.75	$181.75	$181.80
7 purchase totals =	$648.07		$700.1690	$700.16	$700.20	$700.20