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 $223.84   7.794%   $241.2861   $241.29   $241.30   $241.30  
  Purchase #2 $152.39   8.253%   $164.9667   $164.97   $164.95   $165.00  
  Purchase #3 $48.80   7.639%   $52.5278   $52.53   $52.55   $52.50  
  Purchase #4 $18.30   7.158%   $19.6099   $19.61   $19.60   $19.60  
  Purchase #5 $95.76   8.648%   $104.0413   $104.04   $104.05   $104.00  
  Purchase #6 $122.34   3.505%   $126.628   $126.63   $126.65   $126.60  
  Purchase #7 $15.33   8.379%   $16.6145   $16.61   $16.60   $16.60  
  7 purchase totals = $676.76       $725.6743   $725.68   $725.70   $725.60