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 $207.95   7.358%   $223.251   $223.25   $223.25   $223.30  
  Purchase #2 $16.98   8.346%   $18.3972   $18.40   $18.40   $18.40  
  Purchase #3 $183.46   5.372%   $193.3155   $193.32   $193.30   $193.30  
  Purchase #4 $250.37   5.468%   $264.0602   $264.06   $264.05   $264.10  
  Purchase #5 $123.88   9.777%   $135.9917   $135.99   $136.00   $136.00  
  Purchase #6 $162.27   8.786%   $176.527   $176.53   $176.55   $176.50  
  Purchase #7 $202.90   4.685%   $212.4059   $212.41   $212.40   $212.40  
  7 purchase totals = $1,147.81       $1,223.9485   $1,223.96   $1,223.95   $1,224.00