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 $174.26   11.517%   $194.3295   $194.33   $194.35   $194.30  
  Purchase #2 $32.90   9.860%   $36.1439   $36.14   $36.15   $36.10  
  Purchase #3 $126.84   4.625%   $132.7064   $132.71   $132.70   $132.70  
  Purchase #4 $250.66   11.535%   $279.5736   $279.57   $279.55   $279.60  
  Purchase #5 $162.49   8.567%   $176.4105   $176.41   $176.40   $176.40  
  Purchase #6 $170.93   7.151%   $183.1532   $183.15   $183.15   $183.20  
  Purchase #7 $53.27   12.423%   $59.8877   $59.89   $59.90   $59.90  
  7 purchase totals = $971.35       $1,062.2048   $1,062.20   $1,062.20   $1,062.20