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 $169.67   12.376%   $190.6684   $190.67   $190.65   $190.70  
  Purchase #2 $101.31   4.326%   $105.6927   $105.69   $105.70   $105.70  
  Purchase #3 $188.90   8.274%   $204.5296   $204.53   $204.55   $204.50  
  Purchase #4 $162.27   3.321%   $167.659   $167.66   $167.65   $167.70  
  Purchase #5 $183.46   13.617%   $208.4417   $208.44   $208.45   $208.40  
  Purchase #6 $167.77   8.492%   $182.017   $182.02   $182.00   $182.00  
  Purchase #7 $127.61   7.140%   $136.7214   $136.72   $136.70   $136.70  
  7 purchase totals = $1,100.99       $1,195.7298   $1,195.73   $1,195.70   $1,195.70