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 $54.93   9.710%   $60.2637   $60.26   $60.25   $60.30  
  Purchase #2 $185.47   12.745%   $209.1082   $209.11   $209.10   $209.10  
  Purchase #3 $80.42   4.283%   $83.8644   $83.86   $83.85   $83.90  
  Purchase #4 $162.51   4.255%   $169.4248   $169.42   $169.40   $169.40  
  Purchase #5 $100.76   5.755%   $106.5587   $106.56   $106.55   $106.60  
  Purchase #6 $240.97   7.686%   $259.491   $259.49   $259.50   $259.50  
  Purchase #7 $203.54   8.682%   $221.2113   $221.21   $221.20   $221.20  
  7 purchase totals = $1,028.60       $1,109.9221   $1,109.91   $1,109.85   $1,110.00