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 $195.77   5.479%   $206.4962   $206.50   $206.50   $206.50  
  Purchase #2 $40.76   7.777%   $43.9299   $43.93   $43.95   $43.90  
  Purchase #3 $160.94   6.447%   $171.3158   $171.32   $171.30   $171.30  
  Purchase #4 $43.81   7.419%   $47.0603   $47.06   $47.05   $47.10  
  Purchase #5 $151.47   12.631%   $170.6022   $170.60   $170.60   $170.60  
  Purchase #6 $188.64   9.549%   $206.6532   $206.65   $206.65   $206.70  
  Purchase #7 $169.54   10.479%   $187.3061   $187.31   $187.30   $187.30  
  7 purchase totals = $950.93       $1,033.3637   $1,033.37   $1,033.35   $1,033.40