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 $233.69   13.262%   $264.682   $264.68   $264.70   $264.70  
  Purchase #2 $72.72   3.815%   $75.4943   $75.49   $75.50   $75.50  
  Purchase #3 $220.36   12.136%   $247.1029   $247.10   $247.10   $247.10  
  Purchase #4 $155.75   11.618%   $173.845   $173.85   $173.85   $173.80  
  Purchase #5 $113.66   3.533%   $117.6756   $117.68   $117.70   $117.70  
  Purchase #6 $82.36   3.818%   $85.5045   $85.50   $85.50   $85.50  
  Purchase #7 $56.45   7.233%   $60.533   $60.53   $60.55   $60.50  
  7 purchase totals = $934.99       $1,024.8373   $1,024.83   $1,024.90   $1,024.80