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 $114.81   7.625%   $123.5643   $123.56   $123.55   $123.60  
  Purchase #2 $232.39   3.423%   $240.3447   $240.34   $240.35   $240.30  
  Purchase #3 $120.64   4.223%   $125.7346   $125.73   $125.75   $125.70  
  Purchase #4 $188.59   12.149%   $211.5018   $211.50   $211.50   $211.50  
  Purchase #5 $112.48   9.732%   $123.4266   $123.43   $123.45   $123.40  
  Purchase #6 $77.61   8.259%   $84.0198   $84.02   $84.00   $84.00  
  Purchase #7 $156.80   12.190%   $175.9139   $175.91   $175.90   $175.90  
  7 purchase totals = $1,003.32       $1,084.5057   $1,084.49   $1,084.50   $1,084.40