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 $87.30   8.295%   $94.5415   $94.54   $94.55   $94.50  
  Purchase #2 $239.29   10.266%   $263.8555   $263.86   $263.85   $263.90  
  Purchase #3 $23.42   3.498%   $24.2392   $24.24   $24.25   $24.20  
  Purchase #4 $250.57   5.671%   $264.7798   $264.78   $264.80   $264.80  
  Purchase #5 $242.34   10.663%   $268.1807   $268.18   $268.20   $268.20  
  Purchase #6 $186.50   7.814%   $201.0731   $201.07   $201.05   $201.10  
  Purchase #7 $196.75   6.586%   $209.708   $209.71   $209.70   $209.70  
  7 purchase totals = $1,226.17       $1,326.3778   $1,326.38   $1,326.40   $1,326.40