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 $68.64   11.326%   $76.4142   $76.41   $76.40   $76.40  
  Purchase #2 $80.38   13.838%   $91.503   $91.50   $91.50   $91.50  
  Purchase #3 $110.32   10.182%   $121.5528   $121.55   $121.55   $121.60  
  Purchase #4 $94.28   8.841%   $102.6153   $102.62   $102.60   $102.60  
  Purchase #5 $229.76   9.107%   $250.6842   $250.68   $250.70   $250.70  
  Purchase #6 $222.58   8.563%   $241.6395   $241.64   $241.65   $241.60  
  Purchase #7 $215.86   10.521%   $238.5706   $238.57   $238.55   $238.60  
  7 purchase totals = $1,021.82       $1,122.9796   $1,122.97   $1,122.95   $1,123.00