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 $88.58   10.333%   $97.733   $97.73   $97.75   $97.70  
  Purchase #2 $212.28   5.443%   $223.8344   $223.83   $223.85   $223.80  
  Purchase #3 $49.63   3.570%   $51.4018   $51.40   $51.40   $51.40  
  Purchase #4 $129.99   4.115%   $135.3391   $135.34   $135.35   $135.30  
  Purchase #5 $239.66   5.151%   $252.0049   $252.00   $252.00   $252.00  
  Purchase #6 $146.42   12.326%   $164.4677   $164.47   $164.45   $164.50  
  Purchase #7 $242.72   6.282%   $257.9677   $257.97   $257.95   $258.00  
  7 purchase totals = $1,109.28       $1,182.7486   $1,182.74   $1,182.75   $1,182.70