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 $67.29   8.571%   $73.0574   $73.06   $73.05   $73.10  
  Purchase #2 $239.69   11.843%   $268.0765   $268.08   $268.10   $268.10  
  Purchase #3 $162.85   3.248%   $168.1394   $168.14   $168.15   $168.10  
  Purchase #4 $245.78   11.418%   $273.8432   $273.84   $273.85   $273.80  
  Purchase #5 $51.28   10.578%   $56.7044   $56.70   $56.70   $56.70  
  Purchase #6 $240.68   9.159%   $262.7239   $262.72   $262.70   $262.70  
  Purchase #7 $183.89   10.664%   $203.5   $203.50   $203.50   $203.50  
  7 purchase totals = $1,191.46       $1,306.0448   $1,306.04   $1,306.05   $1,306.00