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 $182.37   7.144%   $195.3985   $195.40   $195.40   $195.40  
  Purchase #2 $117.68   7.194%   $126.1459   $126.15   $126.15   $126.10  
  Purchase #3 $190.88   6.234%   $202.7795   $202.78   $202.80   $202.80  
  Purchase #4 $175.62   4.394%   $183.3367   $183.34   $183.35   $183.30  
  Purchase #5 $16.35   12.159%   $18.338   $18.34   $18.35   $18.30  
  Purchase #6 $105.47   11.167%   $117.2478   $117.25   $117.25   $117.20  
  Purchase #7 $77.49   6.779%   $82.743   $82.74   $82.75   $82.70  
  7 purchase totals = $865.86       $925.9894   $926.00   $926.05   $925.80