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 $212.76   6.366%   $226.3043   $226.30   $226.30   $226.30  
  Purchase #2 $148.58   10.143%   $163.6505   $163.65   $163.65   $163.70  
  Purchase #3 $243.31   7.504%   $261.568   $261.57   $261.55   $261.60  
  Purchase #4 $157.89   7.692%   $170.0349   $170.03   $170.05   $170.00  
  Purchase #5 $34.32   11.216%   $38.1693   $38.17   $38.15   $38.20  
  Purchase #6 $63.77   9.789%   $70.0124   $70.01   $70.00   $70.00  
  Purchase #7 $174.62   4.713%   $182.8498   $182.85   $182.85   $182.80  
  7 purchase totals = $1,035.25       $1,112.5892   $1,112.58   $1,112.55   $1,112.60