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 $25.37   3.760%   $26.3239   $26.32   $26.30   $26.30  
  Purchase #2 $214.79   6.721%   $229.226   $229.23   $229.25   $229.20  
  Purchase #3 $62.76   6.865%   $67.0685   $67.07   $67.05   $67.10  
  Purchase #4 $205.85   12.653%   $231.8962   $231.90   $231.90   $231.90  
  Purchase #5 $204.99   3.267%   $211.687   $211.69   $211.70   $211.70  
  Purchase #6 $146.80   5.847%   $155.3834   $155.38   $155.40   $155.40  
  Purchase #7 $122.93   11.134%   $136.617   $136.62   $136.60   $136.60  
  7 purchase totals = $983.49       $1,058.2020   $1,058.21   $1,058.20   $1,058.20