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 $67.45   8.258%   $73.02   $73.02   $73.00   $73.00  
  Purchase #2 $193.36   9.605%   $211.9322   $211.93   $211.95   $211.90  
  Purchase #3 $74.39   3.383%   $76.9066   $76.91   $76.90   $76.90  
  Purchase #4 $213.85   5.452%   $225.5091   $225.51   $225.50   $225.50  
  Purchase #5 $225.73   11.825%   $252.4226   $252.42   $252.40   $252.40  
  Purchase #6 $148.87   4.487%   $155.5498   $155.55   $155.55   $155.50  
  Purchase #7 $122.40   7.581%   $131.6791   $131.68   $131.70   $131.70  
  7 purchase totals = $1,046.05       $1,127.0194   $1,127.02   $1,127.00   $1,126.90