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 $86.40   10.189%   $95.2033   $95.20   $95.20   $95.20  
  Purchase #2 $141.67   9.850%   $155.6245   $155.62   $155.60   $155.60  
  Purchase #3 $167.31   3.715%   $173.5256   $173.53   $173.55   $173.50  
  Purchase #4 $232.54   4.347%   $242.6485   $242.65   $242.65   $242.60  
  Purchase #5 $202.54   11.194%   $225.2123   $225.21   $225.20   $225.20  
  Purchase #6 $180.72   5.156%   $190.0379   $190.04   $190.05   $190.00  
  Purchase #7 $153.47   9.691%   $168.3428   $168.34   $168.35   $168.30  
  7 purchase totals = $1,164.65       $1,250.5949   $1,250.59   $1,250.60   $1,250.40