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 $212.29   11.247%   $236.1663   $236.17   $236.15   $236.20  
  Purchase #2 $242.25   3.708%   $251.2326   $251.23   $251.25   $251.20  
  Purchase #3 $228.85   3.318%   $236.4432   $236.44   $236.45   $236.40  
  Purchase #4 $231.76   3.478%   $239.8206   $239.82   $239.80   $239.80  
  Purchase #5 $65.79   8.850%   $71.6124   $71.61   $71.60   $71.60  
  Purchase #6 $182.50   6.791%   $194.8936   $194.89   $194.90   $194.90  
  Purchase #7 $99.51   11.438%   $110.892   $110.89   $110.90   $110.90  
  7 purchase totals = $1,262.95       $1,341.0607   $1,341.05   $1,341.05   $1,341.00