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 $132.69   6.824%   $141.7448   $141.74   $141.75   $141.70  
  Purchase #2 $10.53   8.444%   $11.4192   $11.42   $11.40   $11.40  
  Purchase #3 $68.42   11.269%   $76.1302   $76.13   $76.15   $76.10  
  Purchase #4 $153.60   11.110%   $170.665   $170.67   $170.65   $170.70  
  Purchase #5 $246.37   10.686%   $272.6971   $272.70   $272.70   $272.70  
  Purchase #6 $123.94   10.425%   $136.8607   $136.86   $136.85   $136.90  
  Purchase #7 $180.95   11.214%   $201.2417   $201.24   $201.25   $201.20  
  7 purchase totals = $916.50       $1,010.7587   $1,010.76   $1,010.75   $1,010.70