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 $206.51   5.201%   $217.2506   $217.25   $217.25   $217.30  
  Purchase #2 $213.53   13.555%   $242.474   $242.47   $242.45   $242.50  
  Purchase #3 $217.97   7.110%   $233.4677   $233.47   $233.45   $233.50  
  Purchase #4 $227.46   5.860%   $240.7892   $240.79   $240.80   $240.80  
  Purchase #5 $154.42   8.255%   $167.1674   $167.17   $167.15   $167.20  
  Purchase #6 $146.44   6.771%   $156.3555   $156.36   $156.35   $156.40  
  Purchase #7 $121.62   3.503%   $125.8803   $125.88   $125.90   $125.90  
  7 purchase totals = $1,287.95       $1,383.3847   $1,383.39   $1,383.35   $1,383.60