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 $182.52   10.432%   $201.5605   $201.56   $201.55   $201.60  
  Purchase #2 $180.33   13.257%   $204.2363   $204.24   $204.25   $204.20  
  Purchase #3 $34.90   4.620%   $36.5124   $36.51   $36.50   $36.50  
  Purchase #4 $42.70   8.554%   $46.3526   $46.35   $46.35   $46.40  
  Purchase #5 $68.25   8.823%   $74.2717   $74.27   $74.25   $74.30  
  Purchase #6 $72.85   3.741%   $75.5753   $75.58   $75.60   $75.60  
  Purchase #7 $238.83   3.161%   $246.3794   $246.38   $246.40   $246.40  
  7 purchase totals = $820.38       $884.8882   $884.89   $884.90   $885.00