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 $58.84   5.795%   $62.2498   $62.25   $62.25   $62.20  
  Purchase #2 $226.45   10.671%   $250.6145   $250.61   $250.60   $250.60  
  Purchase #3 $143.74   5.529%   $151.6874   $151.69   $151.70   $151.70  
  Purchase #4 $179.34   13.523%   $203.5921   $203.59   $203.60   $203.60  
  Purchase #5 $35.40   7.149%   $37.9307   $37.93   $37.95   $37.90  
  Purchase #6 $188.35   12.409%   $211.7224   $211.72   $211.70   $211.70  
  Purchase #7 $158.89   10.744%   $175.9611   $175.96   $175.95   $176.00  
  7 purchase totals = $991.01       $1,093.7580   $1,093.75   $1,093.75   $1,093.70