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 $41.51   5.129%   $43.639   $43.64   $43.65   $43.60  
  Purchase #2 $173.77   5.112%   $182.6531   $182.65   $182.65   $182.70  
  Purchase #3 $211.81   13.859%   $241.1647   $241.16   $241.15   $241.20  
  Purchase #4 $72.99   5.248%   $76.8205   $76.82   $76.80   $76.80  
  Purchase #5 $123.90   12.840%   $139.8088   $139.81   $139.80   $139.80  
  Purchase #6 $108.70   11.152%   $120.8222   $120.82   $120.80   $120.80  
  Purchase #7 $148.83   4.655%   $155.758   $155.76   $155.75   $155.80  
  7 purchase totals = $881.51       $960.6663   $960.66   $960.60   $960.70