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 $59.27   6.524%   $63.1368   $63.14   $63.15   $63.10  
  Purchase #2 $161.38   7.623%   $173.682   $173.68   $173.70   $173.70  
  Purchase #3 $120.76   12.273%   $135.5809   $135.58   $135.60   $135.60  
  Purchase #4 $24.31   13.297%   $27.5425   $27.54   $27.55   $27.50  
  Purchase #5 $220.51   10.319%   $243.2644   $243.26   $243.25   $243.30  
  Purchase #6 $71.31   8.102%   $77.0875   $77.09   $77.10   $77.10  
  Purchase #7 $202.75   11.828%   $226.7313   $226.73   $226.75   $226.70  
  7 purchase totals = $860.29       $947.0254   $947.02   $947.10   $947.00