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 $91.84   3.176%   $94.7568   $94.76   $94.75   $94.80  
  Purchase #2 $172.48   12.184%   $193.495   $193.50   $193.50   $193.50  
  Purchase #3 $111.50   5.149%   $117.2411   $117.24   $117.25   $117.20  
  Purchase #4 $149.54   11.787%   $167.1663   $167.17   $167.15   $167.20  
  Purchase #5 $103.73   4.723%   $108.6292   $108.63   $108.65   $108.60  
  Purchase #6 $216.92   5.398%   $228.6293   $228.63   $228.65   $228.60  
  Purchase #7 $145.51   13.608%   $165.311   $165.31   $165.30   $165.30  
  7 purchase totals = $991.52       $1,075.2287   $1,075.24   $1,075.25   $1,075.20