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 $66.99   6.523%   $71.3598   $71.36   $71.35   $71.40  
  Purchase #2 $101.37   5.666%   $107.1136   $107.11   $107.10   $107.10  
  Purchase #3 $165.81   4.436%   $173.1653   $173.17   $173.15   $173.20  
  Purchase #4 $167.28   12.612%   $188.3774   $188.38   $188.40   $188.40  
  Purchase #5 $190.54   8.581%   $206.8902   $206.89   $206.90   $206.90  
  Purchase #6 $148.32   11.258%   $165.0179   $165.02   $165.00   $165.00  
  Purchase #7 $143.68   6.488%   $153.002   $153.00   $153.00   $153.00  
  7 purchase totals = $983.99       $1,064.9262   $1,064.93   $1,064.90   $1,065.00