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 $87.39   9.392%   $95.5977   $95.60   $95.60   $95.60  
  Purchase #2 $125.73   4.429%   $131.2986   $131.30   $131.30   $131.30  
  Purchase #3 $230.88   9.548%   $252.9244   $252.92   $252.90   $252.90  
  Purchase #4 $216.34   5.851%   $228.9981   $229.00   $229.00   $229.00  
  Purchase #5 $237.34   12.437%   $266.858   $266.86   $266.85   $266.90  
  Purchase #6 $71.85   9.672%   $78.7993   $78.80   $78.80   $78.80  
  Purchase #7 $26.76   6.600%   $28.5262   $28.53   $28.55   $28.50  
  7 purchase totals = $996.29       $1,083.0023   $1,083.01   $1,083.00   $1,083.00