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 $92.93   3.159%   $95.8657   $95.87   $95.85   $95.90  
  Purchase #2 $194.51   3.364%   $201.0533   $201.05   $201.05   $201.10  
  Purchase #3 $73.87   11.319%   $82.2313   $82.23   $82.25   $82.20  
  Purchase #4 $25.94   12.801%   $29.2606   $29.26   $29.25   $29.30  
  Purchase #5 $102.98   5.271%   $108.4081   $108.41   $108.40   $108.40  
  Purchase #6 $34.51   4.258%   $35.9794   $35.98   $36.00   $36.00  
  Purchase #7 $208.63   7.336%   $223.9351   $223.94   $223.95   $223.90  
  7 purchase totals = $733.37       $776.7335   $776.74   $776.75   $776.80