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 $161.27   3.541%   $166.9806   $166.98   $167.00   $167.00  
  Purchase #2 $56.59   5.824%   $59.8858   $59.89   $59.90   $59.90  
  Purchase #3 $187.33   10.513%   $207.024   $207.02   $207.00   $207.00  
  Purchase #4 $17.26   8.106%   $18.6591   $18.66   $18.65   $18.70  
  Purchase #5 $33.64   5.118%   $35.3617   $35.36   $35.35   $35.40  
  Purchase #6 $47.62   11.642%   $53.1639   $53.16   $53.15   $53.20  
  Purchase #7 $209.38   5.383%   $220.6509   $220.65   $220.65   $220.70  
  7 purchase totals = $713.09       $761.7260   $761.72   $761.70   $761.90