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 $82.33   13.758%   $93.657   $93.66   $93.65   $93.70  
  Purchase #2 $234.86   13.769%   $267.1979   $267.20   $267.20   $267.20  
  Purchase #3 $179.38   6.852%   $191.6711   $191.67   $191.65   $191.70  
  Purchase #4 $140.49   8.555%   $152.5089   $152.51   $152.50   $152.50  
  Purchase #5 $112.69   13.706%   $128.1353   $128.14   $128.15   $128.10  
  Purchase #6 $211.48   6.419%   $225.0549   $225.05   $225.05   $225.10  
  Purchase #7 $193.85   9.624%   $212.5061   $212.51   $212.50   $212.50  
  7 purchase totals = $1,155.08       $1,270.7312   $1,270.74   $1,270.70   $1,270.80