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 $125.63   13.621%   $142.7421   $142.74   $142.75   $142.70  
  Purchase #2 $201.96   12.484%   $227.1727   $227.17   $227.15   $227.20  
  Purchase #3 $215.41   13.439%   $244.3589   $244.36   $244.35   $244.40  
  Purchase #4 $195.94   4.346%   $204.4556   $204.46   $204.45   $204.50  
  Purchase #5 $112.35   4.828%   $117.7743   $117.77   $117.75   $117.80  
  Purchase #6 $47.96   3.352%   $49.5676   $49.57   $49.55   $49.60  
  Purchase #7 $54.73   13.248%   $61.9806   $61.98   $62.00   $62.00  
  7 purchase totals = $953.98       $1,048.0518   $1,048.05   $1,048.00   $1,048.20