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 $213.98   10.114%   $235.6219   $235.62   $235.60   $235.60  
  Purchase #2 $149.92   9.132%   $163.6107   $163.61   $163.60   $163.60  
  Purchase #3 $122.67   7.306%   $131.6323   $131.63   $131.65   $131.60  
  Purchase #4 $60.69   8.706%   $65.9737   $65.97   $65.95   $66.00  
  Purchase #5 $194.60   13.360%   $220.5986   $220.60   $220.60   $220.60  
  Purchase #6 $150.71   4.483%   $157.4663   $157.47   $157.45   $157.50  
  Purchase #7 $69.47   3.183%   $71.6812   $71.68   $71.70   $71.70  
  7 purchase totals = $962.04       $1,046.5847   $1,046.58   $1,046.55   $1,046.60