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 $59.69   3.164%   $61.5786   $61.58   $61.60   $61.60  
  Purchase #2 $51.67   8.430%   $56.0258   $56.03   $56.05   $56.00  
  Purchase #3 $159.97   4.804%   $167.655   $167.66   $167.65   $167.70  
  Purchase #4 $60.86   6.623%   $64.8908   $64.89   $64.90   $64.90  
  Purchase #5 $152.37   4.570%   $159.3333   $159.33   $159.35   $159.30  
  Purchase #6 $140.30   6.430%   $149.3213   $149.32   $149.30   $149.30  
  Purchase #7 $187.37   7.496%   $201.4153   $201.42   $201.40   $201.40  
  7 purchase totals = $812.23       $860.2201   $860.23   $860.25   $860.20