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	$143.53	6.105%	$152.2925	$152.29	$152.30	$152.30
Purchase #2	$141.53	3.401%	$146.3434	$146.34	$146.35	$146.30
Purchase #3	$75.35	13.302%	$85.3731	$85.37	$85.35	$85.40
Purchase #4	$202.79	6.259%	$215.4826	$215.48	$215.50	$215.50
Purchase #5	$185.57	11.296%	$206.532	$206.53	$206.55	$206.50
Purchase #6	$112.89	4.356%	$117.8075	$117.81	$117.80	$117.80
Purchase #7	$156.32	10.577%	$172.854	$172.85	$172.85	$172.90
7 purchase totals =	$1,017.98		$1,096.6851	$1,096.67	$1,096.70	$1,096.70