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 $97.93   10.253%   $107.9708   $107.97   $107.95   $108.00  
  Purchase #2 $164.85   13.265%   $186.7174   $186.72   $186.70   $186.70  
  Purchase #3 $159.44   3.182%   $164.5134   $164.51   $164.50   $164.50  
  Purchase #4 $7.98   8.116%   $8.6277   $8.63   $8.65   $8.60  
  Purchase #5 $205.53   4.355%   $214.4808   $214.48   $214.50   $214.50  
  Purchase #6 $165.50   3.259%   $170.8936   $170.89   $170.90   $170.90  
  Purchase #7 $210.60   5.514%   $222.2125   $222.21   $222.20   $222.20  
  7 purchase totals = $1,011.83       $1,075.4162   $1,075.41   $1,075.40   $1,075.40