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 $44.65   5.685%   $47.1884   $47.19   $47.20   $47.20  
  Purchase #2 $181.70   3.712%   $188.4447   $188.44   $188.45   $188.40  
  Purchase #3 $80.80   3.500%   $83.628   $83.63   $83.65   $83.60  
  Purchase #4 $205.49   3.249%   $212.1664   $212.17   $212.15   $212.20  
  Purchase #5 $197.85   4.728%   $207.2043   $207.20   $207.20   $207.20  
  Purchase #6 $107.60   11.350%   $119.8126   $119.81   $119.80   $119.80  
  Purchase #7 $16.26   10.741%   $18.0065   $18.01   $18.00   $18.00  
  7 purchase totals = $834.35       $876.4509   $876.45   $876.45   $876.40