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 $72.27   6.441%   $76.9249   $76.92   $76.90   $76.90  
  Purchase #2 $194.39   7.474%   $208.9187   $208.92   $208.90   $208.90  
  Purchase #3 $162.41   4.127%   $169.1127   $169.11   $169.10   $169.10  
  Purchase #4 $56.80   8.794%   $61.795   $61.80   $61.80   $61.80  
  Purchase #5 $22.74   9.855%   $24.981   $24.98   $25.00   $25.00  
  Purchase #6 $38.67   5.521%   $40.805   $40.81   $40.80   $40.80  
  Purchase #7 $182.95   10.821%   $202.747   $202.75   $202.75   $202.70  
  7 purchase totals = $730.23       $785.2843   $785.29   $785.25   $785.20