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 $52.86   7.548%   $56.8499   $56.85   $56.85   $56.80  
  Purchase #2 $102.44   7.624%   $110.25   $110.25   $110.25   $110.30  
  Purchase #3 $53.27   7.389%   $57.2061   $57.21   $57.20   $57.20  
  Purchase #4 $83.61   10.822%   $92.6583   $92.66   $92.65   $92.70  
  Purchase #5 $70.65   8.445%   $76.6164   $76.62   $76.60   $76.60  
  Purchase #6 $74.51   6.728%   $79.523   $79.52   $79.50   $79.50  
  Purchase #7 $211.86   8.798%   $230.4994   $230.50   $230.50   $230.50  
  7 purchase totals = $649.20       $703.6031   $703.61   $703.55   $703.60