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 $88.75   8.462%   $96.26   $96.26   $96.25   $96.30  
  Purchase #2 $164.36   4.255%   $171.3535   $171.35   $171.35   $171.40  
  Purchase #3 $22.75   8.806%   $24.7534   $24.75   $24.75   $24.80  
  Purchase #4 $64.40   7.271%   $69.0825   $69.08   $69.10   $69.10  
  Purchase #5 $20.28   4.429%   $21.1782   $21.18   $21.20   $21.20  
  Purchase #6 $169.35   5.788%   $179.152   $179.15   $179.15   $179.20  
  Purchase #7 $124.97   8.156%   $135.1626   $135.16   $135.15   $135.20  
  7 purchase totals = $654.86       $696.9422   $696.93   $696.95   $697.20