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 $40.27   8.270%   $43.6003   $43.60   $43.60   $43.60  
  Purchase #2 $47.75   10.568%   $52.7962   $52.80   $52.80   $52.80  
  Purchase #3 $69.91   10.227%   $77.0597   $77.06   $77.05   $77.10  
  Purchase #4 $91.43   9.740%   $100.3353   $100.34   $100.35   $100.30  
  Purchase #5 $102.76   12.790%   $115.903   $115.90   $115.90   $115.90  
  Purchase #6 $195.36   3.258%   $201.7248   $201.72   $201.70   $201.70  
  Purchase #7 $143.62   12.838%   $162.0579   $162.06   $162.05   $162.10  
  7 purchase totals = $691.10       $753.4772   $753.48   $753.45   $753.50