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 $84.34   11.746%   $94.2466   $94.25   $94.25   $94.20  
  Purchase #2 $25.86   3.170%   $26.6798   $26.68   $26.70   $26.70  
  Purchase #3 $88.33   5.307%   $93.0177   $93.02   $93.00   $93.00  
  Purchase #4 $12.95   13.208%   $14.6604   $14.66   $14.65   $14.70  
  Purchase #5 $71.32   10.336%   $78.6916   $78.69   $78.70   $78.70  
  Purchase #6 $232.56   7.410%   $249.7927   $249.79   $249.80   $249.80  
  Purchase #7 $161.55   10.464%   $178.4546   $178.45   $178.45   $178.50  
  7 purchase totals = $676.91       $735.5434   $735.54   $735.55   $735.60