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 $113.51   8.135%   $122.744   $122.74   $122.75   $122.70  
  Purchase #2 $40.37   12.866%   $45.564   $45.56   $45.55   $45.60  
  Purchase #3 $62.96   4.225%   $65.6201   $65.62   $65.60   $65.60  
  Purchase #4 $248.67   11.168%   $276.4415   $276.44   $276.45   $276.40  
  Purchase #5 $55.52   11.513%   $61.912   $61.91   $61.90   $61.90  
  Purchase #6 $207.67   11.340%   $231.2198   $231.22   $231.20   $231.20  
  Purchase #7 $45.51   8.119%   $49.205   $49.21   $49.20   $49.20  
  7 purchase totals = $774.21       $852.7064   $852.70   $852.65   $852.60