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 $101.52   5.463%   $107.066   $107.07   $107.05   $107.10  
  Purchase #2 $70.47   8.839%   $76.6988   $76.70   $76.70   $76.70  
  Purchase #3 $6.26   7.176%   $6.7092   $6.71   $6.70   $6.70  
  Purchase #4 $29.78   6.744%   $31.7884   $31.79   $31.80   $31.80  
  Purchase #5 $226.45   4.773%   $237.2585   $237.26   $237.25   $237.30  
  Purchase #6 $108.89   12.130%   $122.0984   $122.10   $122.10   $122.10  
  Purchase #7 $157.92   4.358%   $164.8022   $164.80   $164.80   $164.80  
  7 purchase totals = $701.29       $746.4215   $746.43   $746.40   $746.50