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 $104.32   9.237%   $113.956   $113.96   $113.95   $114.00  
  Purchase #2 $115.47   8.568%   $125.3635   $125.36   $125.35   $125.40  
  Purchase #3 $244.42   4.701%   $255.9102   $255.91   $255.90   $255.90  
  Purchase #4 $115.39   13.242%   $130.6699   $130.67   $130.65   $130.70  
  Purchase #5 $111.95   11.830%   $125.1937   $125.19   $125.20   $125.20  
  Purchase #6 $231.49   11.794%   $258.7919   $258.79   $258.80   $258.80  
  Purchase #7 $58.94   10.670%   $65.2289   $65.23   $65.25   $65.20  
  7 purchase totals = $981.98       $1,075.1141   $1,075.11   $1,075.10   $1,075.20