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 $23.73   9.820%   $26.0603   $26.06   $26.05   $26.10  
  Purchase #2 $52.56   12.621%   $59.1936   $59.19   $59.20   $59.20  
  Purchase #3 $208.25   11.269%   $231.7177   $231.72   $231.70   $231.70  
  Purchase #4 $143.49   3.161%   $148.0257   $148.03   $148.05   $148.00  
  Purchase #5 $236.61   7.826%   $255.1271   $255.13   $255.15   $255.10  
  Purchase #6 $243.55   4.452%   $254.3928   $254.39   $254.40   $254.40  
  Purchase #7 $101.92   8.596%   $110.681   $110.68   $110.70   $110.70  
  7 purchase totals = $1,010.11       $1,085.1982   $1,085.20   $1,085.25   $1,085.20