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 $65.45   10.421%   $72.2705   $72.27   $72.25   $72.30  
  Purchase #2 $214.49   12.688%   $241.7045   $241.70   $241.70   $241.70  
  Purchase #3 $221.54   6.696%   $236.3743   $236.37   $236.35   $236.40  
  Purchase #4 $26.52   10.705%   $29.359   $29.36   $29.35   $29.40  
  Purchase #5 $129.91   3.847%   $134.9076   $134.91   $134.90   $134.90  
  Purchase #6 $182.33   5.376%   $192.1321   $192.13   $192.15   $192.10  
  Purchase #7 $179.53   13.257%   $203.3303   $203.33   $203.35   $203.30  
  7 purchase totals = $1,019.77       $1,110.0783   $1,110.07   $1,110.05   $1,110.10