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 $62.58   11.439%   $69.7385   $69.74   $69.75   $69.70  
  Purchase #2 $131.89   4.326%   $137.5956   $137.60   $137.60   $137.60  
  Purchase #3 $169.69   13.531%   $192.6508   $192.65   $192.65   $192.70  
  Purchase #4 $122.75   12.672%   $138.3049   $138.30   $138.30   $138.30  
  Purchase #5 $232.39   3.136%   $239.6778   $239.68   $239.70   $239.70  
  Purchase #6 $63.93   11.365%   $71.1956   $71.20   $71.20   $71.20  
  Purchase #7 $10.93   7.864%   $11.7895   $11.79   $11.80   $11.80  
  7 purchase totals = $794.16       $860.9527   $860.96   $861.00   $861.00