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 $61.33   3.843%   $63.6869   $63.69   $63.70   $63.70  
  Purchase #2 $226.58   5.617%   $239.307   $239.31   $239.30   $239.30  
  Purchase #3 $153.93   8.270%   $166.66   $166.66   $166.65   $166.70  
  Purchase #4 $201.32   9.591%   $220.6286   $220.63   $220.65   $220.60  
  Purchase #5 $66.49   13.576%   $75.5167   $75.52   $75.50   $75.50  
  Purchase #6 $142.87   6.226%   $151.7651   $151.77   $151.75   $151.80  
  Purchase #7 $240.33   10.342%   $265.1849   $265.18   $265.20   $265.20  
  7 purchase totals = $1,092.85       $1,182.7492   $1,182.76   $1,182.75   $1,182.80