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 $213.91   5.246%   $225.1317   $225.13   $225.15   $225.10  
  Purchase #2 $216.27   7.273%   $231.9993   $232.00   $232.00   $232.00  
  Purchase #3 $223.92   4.462%   $233.9113   $233.91   $233.90   $233.90  
  Purchase #4 $164.91   9.582%   $180.7117   $180.71   $180.70   $180.70  
  Purchase #5 $13.80   11.236%   $15.3506   $15.35   $15.35   $15.40  
  Purchase #6 $172.56   13.610%   $196.0454   $196.05   $196.05   $196.00  
  Purchase #7 $148.50   6.687%   $158.4302   $158.43   $158.45   $158.40  
  7 purchase totals = $1,153.87       $1,241.5802   $1,241.58   $1,241.60   $1,241.50