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 $235.61   5.271%   $248.029   $248.03   $248.05   $248.00  
  Purchase #2 $216.46   6.276%   $230.045   $230.05   $230.05   $230.00  
  Purchase #3 $58.62   5.237%   $61.6899   $61.69   $61.70   $61.70  
  Purchase #4 $50.27   13.290%   $56.9509   $56.95   $56.95   $57.00  
  Purchase #5 $151.80   9.180%   $165.7352   $165.74   $165.75   $165.70  
  Purchase #6 $234.56   8.368%   $254.188   $254.19   $254.20   $254.20  
  Purchase #7 $77.60   13.275%   $87.9014   $87.90   $87.90   $87.90  
  7 purchase totals = $1,024.92       $1,104.5394   $1,104.55   $1,104.60   $1,104.50