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 $103.71   9.439%   $113.4992   $113.50   $113.50   $113.50  
  Purchase #2 $226.53   10.183%   $249.5975   $249.60   $249.60   $249.60  
  Purchase #3 $62.48   6.709%   $66.6718   $66.67   $66.65   $66.70  
  Purchase #4 $232.28   11.801%   $259.6914   $259.69   $259.70   $259.70  
  Purchase #5 $113.93   6.695%   $121.5576   $121.56   $121.55   $121.60  
  Purchase #6 $211.65   6.737%   $225.9089   $225.91   $225.90   $225.90  
  Purchase #7 $16.87   5.418%   $17.784   $17.78   $17.80   $17.80  
  7 purchase totals = $967.45       $1,054.7104   $1,054.71   $1,054.70   $1,054.80