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 $84.71   12.579%   $95.3657   $95.37   $95.35   $95.40  
  Purchase #2 $192.52   5.817%   $203.7189   $203.72   $203.70   $203.70  
  Purchase #3 $241.44   3.229%   $249.2361   $249.24   $249.25   $249.20  
  Purchase #4 $130.54   6.742%   $139.341   $139.34   $139.35   $139.30  
  Purchase #5 $89.45   3.498%   $92.579   $92.58   $92.60   $92.60  
  Purchase #6 $167.51   4.574%   $175.1719   $175.17   $175.15   $175.20  
  Purchase #7 $190.60   3.719%   $197.6884   $197.69   $197.70   $197.70  
  7 purchase totals = $1,096.77       $1,153.1010   $1,153.11   $1,153.10   $1,153.10