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 $90.96   4.814%   $95.3388   $95.34   $95.35   $95.30  
  Purchase #2 $114.77   5.774%   $121.3968   $121.40   $121.40   $121.40  
  Purchase #3 $226.42   11.726%   $252.97   $252.97   $252.95   $253.00  
  Purchase #4 $210.90   12.519%   $237.3026   $237.30   $237.30   $237.30  
  Purchase #5 $138.33   4.535%   $144.6033   $144.60   $144.60   $144.60  
  Purchase #6 $125.83   8.298%   $136.2714   $136.27   $136.25   $136.30  
  Purchase #7 $137.48   6.304%   $146.1467   $146.15   $146.15   $146.10  
  7 purchase totals = $1,044.69       $1,134.0296   $1,134.03   $1,134.00   $1,134.00