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 $168.58   7.457%   $181.151   $181.15   $181.15   $181.20  
  Purchase #2 $232.62   7.793%   $250.7481   $250.75   $250.75   $250.70  
  Purchase #3 $70.33   10.838%   $77.9524   $77.95   $77.95   $78.00  
  Purchase #4 $173.64   9.751%   $190.5716   $190.57   $190.55   $190.60  
  Purchase #5 $190.66   9.297%   $208.3857   $208.39   $208.40   $208.40  
  Purchase #6 $144.99   11.734%   $162.0031   $162.00   $162.00   $162.00  
  Purchase #7 $33.73   4.489%   $35.2441   $35.24   $35.25   $35.20  
  7 purchase totals = $1,014.55       $1,106.0560   $1,106.05   $1,106.05   $1,106.10