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 $114.67   6.604%   $122.2428   $122.24   $122.25   $122.20  
  Purchase #2 $53.63   8.828%   $58.3645   $58.36   $58.35   $58.40  
  Purchase #3 $85.85   11.373%   $95.6137   $95.61   $95.60   $95.60  
  Purchase #4 $171.94   13.136%   $194.526   $194.53   $194.55   $194.50  
  Purchase #5 $234.78   6.848%   $250.8577   $250.86   $250.85   $250.90  
  Purchase #6 $141.26   3.685%   $146.4654   $146.47   $146.45   $146.50  
  Purchase #7 $146.68   13.753%   $166.8529   $166.85   $166.85   $166.90  
  7 purchase totals = $948.81       $1,034.9230   $1,034.92   $1,034.90   $1,035.00