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 $60.95   10.870%   $67.5753   $67.58   $67.60   $67.60  
  Purchase #2 $109.53   11.420%   $122.0383   $122.04   $122.05   $122.00  
  Purchase #3 $132.40   5.764%   $140.0315   $140.03   $140.05   $140.00  
  Purchase #4 $111.26   13.584%   $126.3736   $126.37   $126.35   $126.40  
  Purchase #5 $134.69   9.581%   $147.5946   $147.59   $147.60   $147.60  
  Purchase #6 $24.51   9.661%   $26.8779   $26.88   $26.90   $26.90  
  Purchase #7 $79.51   10.654%   $87.981   $87.98   $88.00   $88.00  
  7 purchase totals = $652.85       $718.4722   $718.47   $718.55   $718.50