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 $95.34   9.732%   $104.6185   $104.62   $104.60   $104.60  
  Purchase #2 $248.28   11.237%   $276.1792   $276.18   $276.20   $276.20  
  Purchase #3 $191.96   3.323%   $198.3388   $198.34   $198.35   $198.30  
  Purchase #4 $102.66   10.723%   $113.6682   $113.67   $113.65   $113.70  
  Purchase #5 $176.57   12.630%   $198.8708   $198.87   $198.85   $198.90  
  Purchase #6 $89.38   8.150%   $96.6645   $96.66   $96.65   $96.70  
  Purchase #7 $201.88   8.386%   $218.8097   $218.81   $218.80   $218.80  
  7 purchase totals = $1,106.07       $1,207.1497   $1,207.15   $1,207.10   $1,207.20