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 $58.69   5.220%   $61.7536   $61.75   $61.75   $61.80  
  Purchase #2 $180.49   5.619%   $190.6317   $190.63   $190.65   $190.60  
  Purchase #3 $143.44   7.474%   $154.1607   $154.16   $154.15   $154.20  
  Purchase #4 $141.87   12.689%   $159.8719   $159.87   $159.85   $159.90  
  Purchase #5 $201.48   6.486%   $214.548   $214.55   $214.55   $214.50  
  Purchase #6 $245.34   8.151%   $265.3377   $265.34   $265.35   $265.30  
  Purchase #7 $153.77   6.861%   $164.3202   $164.32   $164.30   $164.30  
  7 purchase totals = $1,125.08       $1,210.6238   $1,210.62   $1,210.60   $1,210.60