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 $194.80   5.756%   $206.0127   $206.01   $206.00   $206.00  
  Purchase #2 $214.68   13.106%   $242.816   $242.82   $242.80   $242.80  
  Purchase #3 $39.57   6.205%   $42.0253   $42.03   $42.05   $42.00  
  Purchase #4 $237.82   5.513%   $250.931   $250.93   $250.95   $250.90  
  Purchase #5 $107.88   13.731%   $122.693   $122.69   $122.70   $122.70  
  Purchase #6 $129.60   4.701%   $135.6925   $135.69   $135.70   $135.70  
  Purchase #7 $63.82   5.296%   $67.1999   $67.20   $67.20   $67.20  
  7 purchase totals = $988.17       $1,067.3704   $1,067.37   $1,067.40   $1,067.30