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 $46.51   4.652%   $48.6736   $48.67   $48.65   $48.70  
  Purchase #2 $5.51   13.760%   $6.2682   $6.27   $6.25   $6.30  
  Purchase #3 $81.65   5.183%   $85.8819   $85.88   $85.90   $85.90  
  Purchase #4 $191.43   11.525%   $213.4923   $213.49   $213.50   $213.50  
  Purchase #5 $222.33   7.591%   $239.2071   $239.21   $239.20   $239.20  
  Purchase #6 $127.56   6.736%   $136.1524   $136.15   $136.15   $136.20  
  Purchase #7 $61.90   5.398%   $65.2414   $65.24   $65.25   $65.20  
  7 purchase totals = $736.89       $794.9169   $794.91   $794.90   $795.00