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 $188.46   9.150%   $205.7041   $205.70   $205.70   $205.70  
  Purchase #2 $80.94   4.718%   $84.7587   $84.76   $84.75   $84.80  
  Purchase #3 $12.84   13.260%   $14.5426   $14.54   $14.55   $14.50  
  Purchase #4 $238.47   10.738%   $264.0769   $264.08   $264.10   $264.10  
  Purchase #5 $207.89   9.436%   $227.5065   $227.51   $227.50   $227.50  
  Purchase #6 $214.79   7.777%   $231.4942   $231.49   $231.50   $231.50  
  Purchase #7 $69.89   5.752%   $73.9101   $73.91   $73.90   $73.90  
  7 purchase totals = $1,013.28       $1,101.9931   $1,101.99   $1,102.00   $1,102.00