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 $76.65   9.503%   $83.934   $83.93   $83.95   $83.90  
  Purchase #2 $126.80   4.529%   $132.5428   $132.54   $132.55   $132.50  
  Purchase #3 $99.48   3.168%   $102.6315   $102.63   $102.65   $102.60  
  Purchase #4 $168.58   6.522%   $179.5748   $179.57   $179.55   $179.60  
  Purchase #5 $195.28   6.487%   $207.9478   $207.95   $207.95   $207.90  
  Purchase #6 $69.28   4.493%   $72.3928   $72.39   $72.40   $72.40  
  Purchase #7 $242.55   6.516%   $258.3546   $258.35   $258.35   $258.40  
  7 purchase totals = $978.62       $1,037.3783   $1,037.36   $1,037.40   $1,037.30