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 $95.83   10.701%   $106.0848   $106.08   $106.10   $106.10  
  Purchase #2 $235.42   12.799%   $265.5514   $265.55   $265.55   $265.60  
  Purchase #3 $112.56   4.725%   $117.8785   $117.88   $117.90   $117.90  
  Purchase #4 $54.44   12.123%   $61.0398   $61.04   $61.05   $61.00  
  Purchase #5 $81.25   4.209%   $84.6698   $84.67   $84.65   $84.70  
  Purchase #6 $176.35   6.498%   $187.8092   $187.81   $187.80   $187.80  
  Purchase #7 $118.94   7.299%   $127.6214   $127.62   $127.60   $127.60  
  7 purchase totals = $874.79       $950.6549   $950.65   $950.65   $950.70