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 $152.85   5.447%   $161.1757   $161.18   $161.20   $161.20  
  Purchase #2 $78.48   8.440%   $85.1037   $85.10   $85.10   $85.10  
  Purchase #3 $142.65   8.281%   $154.4628   $154.46   $154.45   $154.50  
  Purchase #4 $250.47   6.565%   $266.9134   $266.91   $266.90   $266.90  
  Purchase #5 $33.33   12.408%   $37.4656   $37.47   $37.45   $37.50  
  Purchase #6 $211.29   11.552%   $235.6982   $235.70   $235.70   $235.70  
  Purchase #7 $93.45   4.565%   $97.716   $97.72   $97.70   $97.70  
  7 purchase totals = $962.52       $1,038.5354   $1,038.54   $1,038.50   $1,038.60