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 $187.91   4.293%   $195.977   $195.98   $196.00   $196.00  
  Purchase #2 $119.27   3.513%   $123.46   $123.46   $123.45   $123.50  
  Purchase #3 $50.90   11.417%   $56.7113   $56.71   $56.70   $56.70  
  Purchase #4 $225.98   9.660%   $247.8097   $247.81   $247.80   $247.80  
  Purchase #5 $136.59   13.462%   $154.9777   $154.98   $155.00   $155.00  
  Purchase #6 $193.43   5.232%   $203.5503   $203.55   $203.55   $203.60  
  Purchase #7 $197.54   8.684%   $214.6944   $214.69   $214.70   $214.70  
  7 purchase totals = $1,111.62       $1,197.1804   $1,197.18   $1,197.20   $1,197.30