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 $84.41   12.752%   $95.174   $95.17   $95.15   $95.20  
  Purchase #2 $224.82   13.824%   $255.8991   $255.90   $255.90   $255.90  
  Purchase #3 $236.26   6.262%   $251.0546   $251.05   $251.05   $251.10  
  Purchase #4 $209.32   12.282%   $235.0287   $235.03   $235.05   $235.00  
  Purchase #5 $128.67   7.174%   $137.9008   $137.90   $137.90   $137.90  
  Purchase #6 $27.31   8.598%   $29.6581   $29.66   $29.65   $29.70  
  Purchase #7 $242.37   5.149%   $254.8496   $254.85   $254.85   $254.80  
  7 purchase totals = $1,153.16       $1,259.5649   $1,259.56   $1,259.55   $1,259.60