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 $61.37   12.525%   $69.0566   $69.06   $69.05   $69.10  
  Purchase #2 $164.57   9.749%   $180.6139   $180.61   $180.60   $180.60  
  Purchase #3 $23.55   11.247%   $26.1987   $26.20   $26.20   $26.20  
  Purchase #4 $97.95   11.406%   $109.1222   $109.12   $109.10   $109.10  
  Purchase #5 $56.80   12.550%   $63.9284   $63.93   $63.95   $63.90  
  Purchase #6 $153.27   12.334%   $172.1743   $172.17   $172.15   $172.20  
  Purchase #7 $225.96   12.808%   $254.901   $254.90   $254.90   $254.90  
  7 purchase totals = $783.47       $875.9951   $875.99   $875.95   $876.00