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 $88.42   7.780%   $95.2991   $95.30   $95.30   $95.30  
  Purchase #2 $244.70   8.512%   $265.5289   $265.53   $265.55   $265.50  
  Purchase #3 $62.87   12.254%   $70.5741   $70.57   $70.55   $70.60  
  Purchase #4 $114.26   9.313%   $124.901   $124.90   $124.90   $124.90  
  Purchase #5 $58.46   6.767%   $62.416   $62.42   $62.40   $62.40  
  Purchase #6 $140.73   8.833%   $153.1607   $153.16   $153.15   $153.20  
  Purchase #7 $154.76   13.337%   $175.4003   $175.40   $175.40   $175.40  
  7 purchase totals = $864.20       $947.2801   $947.28   $947.25   $947.30