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 $232.92   10.554%   $257.5024   $257.50   $257.50   $257.50  
  Purchase #2 $246.62   6.284%   $262.1176   $262.12   $262.10   $262.10  
  Purchase #3 $46.72   5.212%   $49.155   $49.16   $49.15   $49.20  
  Purchase #4 $74.34   6.323%   $79.0405   $79.04   $79.05   $79.00  
  Purchase #5 $168.89   7.798%   $182.06   $182.06   $182.05   $182.10  
  Purchase #6 $197.59   3.150%   $203.8141   $203.81   $203.80   $203.80  
  Purchase #7 $107.48   4.598%   $112.4219   $112.42   $112.40   $112.40  
  7 purchase totals = $1,074.56       $1,146.1115   $1,146.11   $1,146.05   $1,146.10