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 $101.38   10.143%   $111.663   $111.66   $111.65   $111.70  
  Purchase #2 $229.75   5.334%   $242.0049   $242.00   $242.00   $242.00  
  Purchase #3 $177.41   7.145%   $190.0859   $190.09   $190.10   $190.10  
  Purchase #4 $150.77   12.543%   $169.6811   $169.68   $169.70   $169.70  
  Purchase #5 $178.26   10.253%   $196.537   $196.54   $196.55   $196.50  
  Purchase #6 $62.52   9.307%   $68.3387   $68.34   $68.35   $68.30  
  Purchase #7 $32.81   9.825%   $36.0336   $36.03   $36.05   $36.00  
  7 purchase totals = $932.90       $1,014.3442   $1,014.34   $1,014.40   $1,014.30