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 $5.76   4.748%   $6.0335   $6.03   $6.05   $6.00  
  Purchase #2 $204.62   12.228%   $229.6409   $229.64   $229.65   $229.60  
  Purchase #3 $48.59   11.686%   $54.2682   $54.27   $54.25   $54.30  
  Purchase #4 $152.42   6.747%   $162.7038   $162.70   $162.70   $162.70  
  Purchase #5 $149.48   3.673%   $154.9704   $154.97   $154.95   $155.00  
  Purchase #6 $235.76   8.581%   $255.9906   $255.99   $256.00   $256.00  
  Purchase #7 $244.57   7.115%   $261.9712   $261.97   $261.95   $262.00  
  7 purchase totals = $1,041.20       $1,125.5786   $1,125.57   $1,125.55   $1,125.60