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 $88.32   8.398%   $95.7371   $95.74   $95.75   $95.70  
  Purchase #2 $61.57   13.286%   $69.7502   $69.75   $69.75   $69.80  
  Purchase #3 $35.60   3.138%   $36.7171   $36.72   $36.70   $36.70  
  Purchase #4 $107.48   12.515%   $120.9311   $120.93   $120.95   $120.90  
  Purchase #5 $215.94   5.403%   $227.6072   $227.61   $227.60   $227.60  
  Purchase #6 $131.66   3.240%   $135.9258   $135.93   $135.95   $135.90  
  Purchase #7 $27.98   11.588%   $31.2223   $31.22   $31.20   $31.20  
  7 purchase totals = $668.55       $717.8908   $717.90   $717.90   $717.80