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 $193.64   10.524%   $214.0187   $214.02   $214.00   $214.00  
  Purchase #2 $43.27   6.299%   $45.9956   $46.00   $46.00   $46.00  
  Purchase #3 $233.40   5.806%   $246.9512   $246.95   $246.95   $247.00  
  Purchase #4 $232.65   11.820%   $260.1492   $260.15   $260.15   $260.10  
  Purchase #5 $100.28   12.744%   $113.0597   $113.06   $113.05   $113.10  
  Purchase #6 $51.73   9.812%   $56.8057   $56.81   $56.80   $56.80  
  Purchase #7 $73.25   10.177%   $80.7047   $80.70   $80.70   $80.70  
  7 purchase totals = $928.22       $1,017.6848   $1,017.69   $1,017.65   $1,017.70