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 $115.74   8.612%   $125.7075   $125.71   $125.70   $125.70  
  Purchase #2 $32.84   10.441%   $36.2688   $36.27   $36.25   $36.30  
  Purchase #3 $157.73   9.175%   $172.2017   $172.20   $172.20   $172.20  
  Purchase #4 $22.88   7.713%   $24.6447   $24.64   $24.65   $24.60  
  Purchase #5 $32.43   7.692%   $34.9245   $34.92   $34.90   $34.90  
  Purchase #6 $177.48   6.381%   $188.805   $188.81   $188.80   $188.80  
  Purchase #7 $164.61   8.229%   $178.1558   $178.16   $178.15   $178.20  
  7 purchase totals = $703.71       $760.7080   $760.71   $760.65   $760.70