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 $126.82   11.811%   $141.7987   $141.80   $141.80   $141.80  
  Purchase #2 $234.60   3.112%   $241.9008   $241.90   $241.90   $241.90  
  Purchase #3 $162.54   8.158%   $175.8   $175.80   $175.80   $175.80  
  Purchase #4 $201.41   3.850%   $209.1643   $209.16   $209.15   $209.20  
  Purchase #5 $148.31   11.628%   $165.5555   $165.56   $165.55   $165.60  
  Purchase #6 $81.99   4.549%   $85.7197   $85.72   $85.70   $85.70  
  Purchase #7 $5.69   12.121%   $6.3797   $6.38   $6.40   $6.40  
  7 purchase totals = $961.36       $1,026.3187   $1,026.32   $1,026.30   $1,026.40