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 $58.64   4.259%   $61.1375   $61.14   $61.15   $61.10  
  Purchase #2 $12.25   3.677%   $12.7004   $12.70   $12.70   $12.70  
  Purchase #3 $92.28   10.593%   $102.0552   $102.06   $102.05   $102.10  
  Purchase #4 $229.26   9.326%   $250.6408   $250.64   $250.65   $250.60  
  Purchase #5 $209.81   11.782%   $234.5298   $234.53   $234.55   $234.50  
  Purchase #6 $149.27   12.268%   $167.5824   $167.58   $167.60   $167.60  
  Purchase #7 $240.87   10.479%   $266.1108   $266.11   $266.10   $266.10  
  7 purchase totals = $992.38       $1,094.7569   $1,094.76   $1,094.80   $1,094.70