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 $56.97   8.553%   $61.8426   $61.84   $61.85   $61.80  
  Purchase #2 $207.40   4.216%   $216.144   $216.14   $216.15   $216.10  
  Purchase #3 $16.45   4.787%   $17.2375   $17.24   $17.25   $17.20  
  Purchase #4 $155.49   3.589%   $161.0705   $161.07   $161.05   $161.10  
  Purchase #5 $162.48   8.560%   $176.3883   $176.39   $176.40   $176.40  
  Purchase #6 $91.78   3.324%   $94.8308   $94.83   $94.85   $94.80  
  Purchase #7 $174.97   7.773%   $188.5704   $188.57   $188.55   $188.60  
  7 purchase totals = $865.54       $916.0841   $916.08   $916.10   $916.00