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 $83.78   13.379%   $94.9889   $94.99   $95.00   $95.00  
  Purchase #2 $195.71   3.609%   $202.7732   $202.77   $202.75   $202.80  
  Purchase #3 $32.65   13.417%   $37.0307   $37.03   $37.05   $37.00  
  Purchase #4 $29.29   12.790%   $33.0362   $33.04   $33.05   $33.00  
  Purchase #5 $156.70   3.200%   $161.7144   $161.71   $161.70   $161.70  
  Purchase #6 $136.38   4.687%   $142.7721   $142.77   $142.75   $142.80  
  Purchase #7 $228.78   12.477%   $257.3249   $257.32   $257.30   $257.30  
  7 purchase totals = $863.29       $929.6404   $929.63   $929.60   $929.60