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 $161.53   4.761%   $169.2204   $169.22   $169.20   $169.20  
  Purchase #2 $179.43   8.694%   $195.0296   $195.03   $195.05   $195.00  
  Purchase #3 $54.63   8.447%   $59.2446   $59.24   $59.25   $59.20  
  Purchase #4 $177.66   11.603%   $198.2739   $198.27   $198.25   $198.30  
  Purchase #5 $164.91   5.559%   $174.0773   $174.08   $174.10   $174.10  
  Purchase #6 $190.79   3.179%   $196.8552   $196.86   $196.85   $196.90  
  Purchase #7 $66.72   12.361%   $74.9673   $74.97   $74.95   $75.00  
  7 purchase totals = $995.67       $1,067.6683   $1,067.67   $1,067.65   $1,067.70