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 $23.35   10.616%   $25.8288   $25.83   $25.85   $25.80  
  Purchase #2 $244.76   6.816%   $261.4428   $261.44   $261.45   $261.40  
  Purchase #3 $160.47   6.830%   $171.4301   $171.43   $171.45   $171.40  
  Purchase #4 $234.74   3.872%   $243.8291   $243.83   $243.85   $243.80  
  Purchase #5 $241.38   12.168%   $270.7511   $270.75   $270.75   $270.80  
  Purchase #6 $248.63   3.782%   $258.0332   $258.03   $258.05   $258.00  
  Purchase #7 $179.39   12.621%   $202.0308   $202.03   $202.05   $202.00  
  7 purchase totals = $1,332.72       $1,433.3459   $1,433.34   $1,433.45   $1,433.20