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 $168.95   6.706%   $180.2798   $180.28   $180.30   $180.30  
  Purchase #2 $187.70   9.383%   $205.3119   $205.31   $205.30   $205.30  
  Purchase #3 $177.28   10.405%   $195.726   $195.73   $195.75   $195.70  
  Purchase #4 $64.99   13.368%   $73.6779   $73.68   $73.70   $73.70  
  Purchase #5 $75.76   13.482%   $85.974   $85.97   $85.95   $86.00  
  Purchase #6 $188.65   11.179%   $209.7392   $209.74   $209.75   $209.70  
  Purchase #7 $232.97   7.601%   $250.678   $250.68   $250.70   $250.70  
  7 purchase totals = $1,096.30       $1,201.3868   $1,201.39   $1,201.45   $1,201.40