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 $196.76   3.655%   $203.9516   $203.95   $203.95   $204.00  
  Purchase #2 $247.81   13.679%   $281.7079   $281.71   $281.70   $281.70  
  Purchase #3 $211.52   8.617%   $229.7467   $229.75   $229.75   $229.70  
  Purchase #4 $83.70   12.770%   $94.3885   $94.39   $94.40   $94.40  
  Purchase #5 $89.74   12.565%   $101.0158   $101.02   $101.00   $101.00  
  Purchase #6 $118.55   6.662%   $126.4478   $126.45   $126.45   $126.40  
  Purchase #7 $154.81   6.359%   $164.6544   $164.65   $164.65   $164.70  
  7 purchase totals = $1,102.89       $1,201.9127   $1,201.92   $1,201.90   $1,201.90