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 $98.83   5.704%   $104.4673   $104.47   $104.45   $104.50  
  Purchase #2 $176.99   8.351%   $191.7704   $191.77   $191.75   $191.80  
  Purchase #3 $150.36   5.669%   $158.8839   $158.88   $158.90   $158.90  
  Purchase #4 $70.49   6.297%   $74.9288   $74.93   $74.95   $74.90  
  Purchase #5 $231.60   5.658%   $244.7039   $244.70   $244.70   $244.70  
  Purchase #6 $124.55   8.348%   $134.9474   $134.95   $134.95   $134.90  
  Purchase #7 $176.88   13.629%   $200.987   $200.99   $201.00   $201.00  
  7 purchase totals = $1,029.70       $1,110.6887   $1,110.69   $1,110.70   $1,110.70