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 $59.48   5.398%   $62.6907   $62.69   $62.70   $62.70  
  Purchase #2 $117.94   9.451%   $129.0865   $129.09   $129.10   $129.10  
  Purchase #3 $225.40   11.231%   $250.7147   $250.71   $250.70   $250.70  
  Purchase #4 $238.30   3.675%   $247.0575   $247.06   $247.05   $247.10  
  Purchase #5 $176.58   3.715%   $183.1399   $183.14   $183.15   $183.10  
  Purchase #6 $239.71   4.666%   $250.8949   $250.89   $250.90   $250.90  
  Purchase #7 $81.96   8.516%   $88.9397   $88.94   $88.95   $88.90  
  7 purchase totals = $1,139.37       $1,212.5239   $1,212.52   $1,212.55   $1,212.50