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 $209.83   3.260%   $216.6705   $216.67   $216.65   $216.70  
  Purchase #2 $217.74   4.297%   $227.0963   $227.10   $227.10   $227.10  
  Purchase #3 $23.67   11.275%   $26.3388   $26.34   $26.35   $26.30  
  Purchase #4 $59.65   6.241%   $63.3728   $63.37   $63.35   $63.40  
  Purchase #5 $74.43   3.707%   $77.1891   $77.19   $77.20   $77.20  
  Purchase #6 $177.80   7.255%   $190.6994   $190.70   $190.70   $190.70  
  Purchase #7 $115.41   7.631%   $124.2169   $124.22   $124.20   $124.20  
  7 purchase totals = $878.53       $925.5838   $925.59   $925.55   $925.60