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 $56.26   10.238%   $62.0199   $62.02   $62.00   $62.00  
  Purchase #2 $17.84   6.508%   $19.001   $19.00   $19.00   $19.00  
  Purchase #3 $175.87   12.740%   $198.2758   $198.28   $198.30   $198.30  
  Purchase #4 $46.82   3.697%   $48.5509   $48.55   $48.55   $48.60  
  Purchase #5 $130.32   4.739%   $136.4959   $136.50   $136.50   $136.50  
  Purchase #6 $86.51   3.833%   $89.8259   $89.83   $89.85   $89.80  
  Purchase #7 $179.72   4.740%   $188.2387   $188.24   $188.25   $188.20  
  7 purchase totals = $693.34       $742.4081   $742.42   $742.45   $742.40