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 $235.47   4.726%   $246.5983   $246.60   $246.60   $246.60  
  Purchase #2 $197.38   13.739%   $224.498   $224.50   $224.50   $224.50  
  Purchase #3 $89.95   6.844%   $96.1062   $96.11   $96.10   $96.10  
  Purchase #4 $164.55   6.696%   $175.5683   $175.57   $175.55   $175.60  
  Purchase #5 $93.85   8.757%   $102.0684   $102.07   $102.05   $102.10  
  Purchase #6 $49.90   13.691%   $56.7318   $56.73   $56.75   $56.70  
  Purchase #7 $233.78   7.395%   $251.068   $251.07   $251.05   $251.10  
  7 purchase totals = $1,064.88       $1,152.6390   $1,152.65   $1,152.60   $1,152.70