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 $207.92   7.342%   $223.1855   $223.19   $223.20   $223.20  
  Purchase #2 $120.35   4.380%   $125.6213   $125.62   $125.60   $125.60  
  Purchase #3 $195.88   13.182%   $221.7009   $221.70   $221.70   $221.70  
  Purchase #4 $167.26   5.264%   $176.0646   $176.06   $176.05   $176.10  
  Purchase #5 $163.71   6.392%   $174.1743   $174.17   $174.15   $174.20  
  Purchase #6 $230.92   11.804%   $258.1778   $258.18   $258.20   $258.20  
  Purchase #7 $78.85   10.416%   $87.063   $87.06   $87.05   $87.10  
  7 purchase totals = $1,164.89       $1,265.9874   $1,265.98   $1,265.95   $1,266.10