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 $61.90   12.411%   $69.5824   $69.58   $69.60   $69.60  
  Purchase #2 $20.75   7.590%   $22.3249   $22.32   $22.30   $22.30  
  Purchase #3 $82.98   13.354%   $94.0611   $94.06   $94.05   $94.10  
  Purchase #4 $9.92   5.277%   $10.4435   $10.44   $10.45   $10.40  
  Purchase #5 $229.52   4.727%   $240.3694   $240.37   $240.35   $240.40  
  Purchase #6 $191.91   8.476%   $208.1763   $208.18   $208.20   $208.20  
  Purchase #7 $222.38   12.464%   $250.0974   $250.10   $250.10   $250.10  
  7 purchase totals = $819.36       $895.0550   $895.05   $895.05   $895.10