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	$211.27	11.768%	$236.1323	$236.13	$236.15	$236.10
Purchase #2	$80.95	8.170%	$87.5636	$87.56	$87.55	$87.60
Purchase #3	$150.76	11.143%	$167.5592	$167.56	$167.55	$167.60
Purchase #4	$68.66	6.237%	$72.9423	$72.94	$72.95	$72.90
Purchase #5	$32.29	4.434%	$33.7217	$33.72	$33.70	$33.70
Purchase #6	$41.85	9.342%	$45.7596	$45.76	$45.75	$45.80
Purchase #7	$202.45	7.486%	$217.6054	$217.61	$217.60	$217.60
7 purchase totals =	$788.23		$861.2841	$861.28	$861.25	$861.30