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 $117.83   7.544%   $126.7191   $126.72   $126.70   $126.70  
  Purchase #2 $173.88   13.399%   $197.1782   $197.18   $197.20   $197.20  
  Purchase #3 $131.76   3.713%   $136.6522   $136.65   $136.65   $136.70  
  Purchase #4 $209.87   6.622%   $223.7676   $223.77   $223.75   $223.80  
  Purchase #5 $72.45   12.163%   $81.2621   $81.26   $81.25   $81.30  
  Purchase #6 $89.31   12.498%   $100.472   $100.47   $100.45   $100.50  
  Purchase #7 $177.55   11.106%   $197.2687   $197.27   $197.25   $197.30  
  7 purchase totals = $972.65       $1,063.3199   $1,063.32   $1,063.25   $1,063.50