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 $65.86   13.786%   $74.9395   $74.94   $74.95   $74.90  
  Purchase #2 $187.25   4.623%   $195.9066   $195.91   $195.90   $195.90  
  Purchase #3 $248.42   11.155%   $276.1313   $276.13   $276.15   $276.10  
  Purchase #4 $145.48   3.830%   $151.0519   $151.05   $151.05   $151.10  
  Purchase #5 $142.32   12.774%   $160.5   $160.50   $160.50   $160.50  
  Purchase #6 $82.91   12.104%   $92.9454   $92.95   $92.95   $92.90  
  Purchase #7 $154.31   5.690%   $163.0902   $163.09   $163.10   $163.10  
  7 purchase totals = $1,026.55       $1,114.5649   $1,114.57   $1,114.60   $1,114.50