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 $209.56   10.669%   $231.918   $231.92   $231.90   $231.90  
  Purchase #2 $85.58   7.115%   $91.669   $91.67   $91.65   $91.70  
  Purchase #3 $188.41   8.403%   $204.2421   $204.24   $204.25   $204.20  
  Purchase #4 $185.66   8.775%   $201.9517   $201.95   $201.95   $202.00  
  Purchase #5 $218.78   13.459%   $248.2256   $248.23   $248.25   $248.20  
  Purchase #6 $5.29   8.365%   $5.7325   $5.73   $5.75   $5.70  
  Purchase #7 $187.86   8.216%   $203.2946   $203.29   $203.30   $203.30  
  7 purchase totals = $1,081.14       $1,187.0335   $1,187.03   $1,187.05   $1,187.00