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 $163.56   11.654%   $182.6213   $182.62   $182.60   $182.60  
  Purchase #2 $55.41   6.477%   $58.9989   $59.00   $59.00   $59.00  
  Purchase #3 $40.74   8.515%   $44.209   $44.21   $44.20   $44.20  
  Purchase #4 $181.81   5.407%   $191.6405   $191.64   $191.65   $191.60  
  Purchase #5 $188.82   8.663%   $205.1775   $205.18   $205.20   $205.20  
  Purchase #6 $240.77   8.288%   $260.725   $260.73   $260.75   $260.70  
  Purchase #7 $203.90   3.697%   $211.4382   $211.44   $211.45   $211.40  
  7 purchase totals = $1,075.01       $1,154.8104   $1,154.82   $1,154.85   $1,154.70