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 $54.49   8.141%   $58.926   $58.93   $58.95   $58.90  
  Purchase #2 $240.31   9.363%   $262.8102   $262.81   $262.80   $262.80  
  Purchase #3 $245.51   8.390%   $266.1083   $266.11   $266.10   $266.10  
  Purchase #4 $93.37   10.362%   $103.045   $103.05   $103.05   $103.00  
  Purchase #5 $16.50   4.665%   $17.2697   $17.27   $17.25   $17.30  
  Purchase #6 $179.36   3.844%   $186.2546   $186.25   $186.25   $186.30  
  Purchase #7 $193.44   13.732%   $220.0032   $220.00   $220.00   $220.00  
  7 purchase totals = $1,022.98       $1,114.4170   $1,114.42   $1,114.40   $1,114.40