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 $169.69   7.431%   $182.2997   $182.30   $182.30   $182.30  
  Purchase #2 $123.72   6.454%   $131.7049   $131.70   $131.70   $131.70  
  Purchase #3 $49.85   13.176%   $56.4182   $56.42   $56.40   $56.40  
  Purchase #4 $119.71   13.352%   $135.6937   $135.69   $135.70   $135.70  
  Purchase #5 $156.57   12.175%   $175.6324   $175.63   $175.65   $175.60  
  Purchase #6 $216.45   5.502%   $228.3591   $228.36   $228.35   $228.40  
  Purchase #7 $245.28   4.557%   $256.4574   $256.46   $256.45   $256.50  
  7 purchase totals = $1,081.27       $1,166.5654   $1,166.56   $1,166.55   $1,166.60