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 $23.86   8.764%   $25.9511   $25.95   $25.95   $26.00  
  Purchase #2 $213.85   6.836%   $228.4688   $228.47   $228.45   $228.50  
  Purchase #3 $239.77   5.818%   $253.7198   $253.72   $253.70   $253.70  
  Purchase #4 $111.31   5.215%   $117.1148   $117.11   $117.10   $117.10  
  Purchase #5 $170.74   13.342%   $193.5201   $193.52   $193.50   $193.50  
  Purchase #6 $225.46   6.655%   $240.4644   $240.46   $240.45   $240.50  
  Purchase #7 $209.42   13.400%   $237.4823   $237.48   $237.50   $237.50  
  7 purchase totals = $1,194.41       $1,296.7213   $1,296.71   $1,296.65   $1,296.80