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 $46.84   7.367%   $50.2907   $50.29   $50.30   $50.30  
  Purchase #2 $250.60   3.172%   $258.549   $258.55   $258.55   $258.50  
  Purchase #3 $119.88   10.572%   $132.5537   $132.55   $132.55   $132.60  
  Purchase #4 $211.91   6.355%   $225.3769   $225.38   $225.40   $225.40  
  Purchase #5 $186.46   7.634%   $200.6944   $200.69   $200.70   $200.70  
  Purchase #6 $152.40   7.210%   $163.388   $163.39   $163.40   $163.40  
  Purchase #7 $165.86   10.758%   $183.7032   $183.70   $183.70   $183.70  
  7 purchase totals = $1,133.95       $1,214.5559   $1,214.55   $1,214.60   $1,214.60