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 $114.41   4.605%   $119.6786   $119.68   $119.70   $119.70  
  Purchase #2 $197.75   9.171%   $215.8857   $215.89   $215.90   $215.90  
  Purchase #3 $69.57   5.338%   $73.2836   $73.28   $73.30   $73.30  
  Purchase #4 $66.39   11.372%   $73.9399   $73.94   $73.95   $73.90  
  Purchase #5 $166.91   12.636%   $188.0007   $188.00   $188.00   $188.00  
  Purchase #6 $65.43   3.760%   $67.8902   $67.89   $67.90   $67.90  
  Purchase #7 $152.72   3.251%   $157.6849   $157.68   $157.70   $157.70  
  7 purchase totals = $833.18       $896.3636   $896.36   $896.45   $896.40