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 $61.39   4.137%   $63.9297   $63.93   $63.95   $63.90  
  Purchase #2 $146.89   3.777%   $152.438   $152.44   $152.45   $152.40  
  Purchase #3 $206.44   13.588%   $234.4911   $234.49   $234.50   $234.50  
  Purchase #4 $114.60   6.370%   $121.9   $121.90   $121.90   $121.90  
  Purchase #5 $169.45   3.223%   $174.9114   $174.91   $174.90   $174.90  
  Purchase #6 $156.73   5.118%   $164.7514   $164.75   $164.75   $164.80  
  Purchase #7 $220.35   4.342%   $229.9176   $229.92   $229.90   $229.90  
  7 purchase totals = $1,075.85       $1,142.3392   $1,142.34   $1,142.35   $1,142.30