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 $64.60   5.419%   $68.1007   $68.10   $68.10   $68.10  
  Purchase #2 $215.96   5.833%   $228.5569   $228.56   $228.55   $228.60  
  Purchase #3 $11.70   13.140%   $13.2374   $13.24   $13.25   $13.20  
  Purchase #4 $94.34   10.177%   $103.941   $103.94   $103.95   $103.90  
  Purchase #5 $155.35   6.278%   $165.1029   $165.10   $165.10   $165.10  
  Purchase #6 $78.89   4.432%   $82.3864   $82.39   $82.40   $82.40  
  Purchase #7 $51.79   6.389%   $55.0989   $55.10   $55.10   $55.10  
  7 purchase totals = $672.63       $716.4242   $716.43   $716.45   $716.40