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 $241.26   9.495%   $264.1676   $264.17   $264.15   $264.20  
  Purchase #2 $162.77   4.597%   $170.2525   $170.25   $170.25   $170.30  
  Purchase #3 $160.31   13.723%   $182.3093   $182.31   $182.30   $182.30  
  Purchase #4 $32.74   3.773%   $33.9753   $33.98   $34.00   $34.00  
  Purchase #5 $200.91   5.394%   $211.7471   $211.75   $211.75   $211.70  
  Purchase #6 $73.55   4.276%   $76.695   $76.70   $76.70   $76.70  
  Purchase #7 $102.37   11.455%   $114.0965   $114.10   $114.10   $114.10  
  7 purchase totals = $973.91       $1,053.2433   $1,053.26   $1,053.25   $1,053.30