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 $184.53   6.592%   $196.6942   $196.69   $196.70   $196.70  
  Purchase #2 $11.46   5.353%   $12.0735   $12.07   $12.05   $12.10  
  Purchase #3 $35.68   6.125%   $37.8654   $37.87   $37.85   $37.90  
  Purchase #4 $246.46   13.775%   $280.4099   $280.41   $280.40   $280.40  
  Purchase #5 $13.54   11.498%   $15.0968   $15.10   $15.10   $15.10  
  Purchase #6 $119.59   10.426%   $132.0585   $132.06   $132.05   $132.10  
  Purchase #7 $188.57   6.802%   $201.3965   $201.40   $201.40   $201.40  
  7 purchase totals = $799.83       $875.5948   $875.60   $875.55   $875.70