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 $46.36   3.675%   $48.0637   $48.06   $48.05   $48.10  
  Purchase #2 $130.29   12.188%   $146.1697   $146.17   $146.15   $146.20  
  Purchase #3 $216.29   10.812%   $239.6753   $239.68   $239.70   $239.70  
  Purchase #4 $8.35   6.386%   $8.8832   $8.88   $8.90   $8.90  
  Purchase #5 $204.27   11.522%   $227.806   $227.81   $227.80   $227.80  
  Purchase #6 $239.67   12.624%   $269.9259   $269.93   $269.95   $269.90  
  Purchase #7 $73.90   10.364%   $81.559   $81.56   $81.55   $81.60  
  7 purchase totals = $919.13       $1,022.0828   $1,022.09   $1,022.10   $1,022.20