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 $47.41   13.759%   $53.9331   $53.93   $53.95   $53.90  
  Purchase #2 $52.86   8.831%   $57.5281   $57.53   $57.55   $57.50  
  Purchase #3 $91.67   7.695%   $98.724   $98.72   $98.70   $98.70  
  Purchase #4 $94.93   13.295%   $107.5509   $107.55   $107.55   $107.60  
  Purchase #5 $116.82   4.415%   $121.9776   $121.98   $122.00   $122.00  
  Purchase #6 $209.62   3.357%   $216.6569   $216.66   $216.65   $216.70  
  Purchase #7 $207.77   8.872%   $226.2034   $226.20   $226.20   $226.20  
  7 purchase totals = $821.08       $882.5740   $882.57   $882.60   $882.60