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 $85.68   11.257%   $95.325   $95.33   $95.35   $95.30  
  Purchase #2 $53.90   6.625%   $57.4709   $57.47   $57.45   $57.50  
  Purchase #3 $153.63   7.871%   $165.7222   $165.72   $165.70   $165.70  
  Purchase #4 $211.69   10.579%   $234.0847   $234.08   $234.10   $234.10  
  Purchase #5 $58.62   7.361%   $62.935   $62.94   $62.95   $62.90  
  Purchase #6 $155.70   10.811%   $172.5327   $172.53   $172.55   $172.50  
  Purchase #7 $182.71   13.800%   $207.924   $207.92   $207.90   $207.90  
  7 purchase totals = $901.93       $995.9945   $995.99   $996.00   $995.90