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 $84.61   13.767%   $96.2583   $96.26   $96.25   $96.30  
  Purchase #2 $201.99   6.307%   $214.7295   $214.73   $214.75   $214.70  
  Purchase #3 $49.42   11.601%   $55.1532   $55.15   $55.15   $55.20  
  Purchase #4 $190.90   12.765%   $215.2684   $215.27   $215.25   $215.30  
  Purchase #5 $182.40   8.418%   $197.7544   $197.75   $197.75   $197.80  
  Purchase #6 $131.37   8.397%   $142.4011   $142.40   $142.40   $142.40  
  Purchase #7 $222.66   4.191%   $231.9917   $231.99   $232.00   $232.00  
  7 purchase totals = $1,063.35       $1,153.5566   $1,153.55   $1,153.55   $1,153.70