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 $59.41   12.690%   $66.9491   $66.95   $66.95   $66.90  
  Purchase #2 $226.86   3.841%   $235.5737   $235.57   $235.55   $235.60  
  Purchase #3 $164.48   11.470%   $183.3459   $183.35   $183.35   $183.30  
  Purchase #4 $195.66   6.102%   $207.5992   $207.60   $207.60   $207.60  
  Purchase #5 $221.26   11.185%   $246.0079   $246.01   $246.00   $246.00  
  Purchase #6 $58.28   9.186%   $63.6336   $63.63   $63.65   $63.60  
  Purchase #7 $134.64   4.580%   $140.8065   $140.81   $140.80   $140.80  
  7 purchase totals = $1,060.59       $1,143.9159   $1,143.92   $1,143.90   $1,143.80