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 $85.87   11.757%   $95.9657   $95.97   $95.95   $96.00  
  Purchase #2 $174.91   6.222%   $185.7929   $185.79   $185.80   $185.80  
  Purchase #3 $187.62   7.293%   $201.3031   $201.30   $201.30   $201.30  
  Purchase #4 $224.38   11.685%   $250.5988   $250.60   $250.60   $250.60  
  Purchase #5 $10.41   13.225%   $11.7867   $11.79   $11.80   $11.80  
  Purchase #6 $189.83   6.618%   $202.3929   $202.39   $202.40   $202.40  
  Purchase #7 $9.47   12.252%   $10.6303   $10.63   $10.65   $10.60  
  7 purchase totals = $882.49       $958.4704   $958.47   $958.50   $958.50