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 $58.34   7.241%   $62.5644   $62.56   $62.55   $62.60  
  Purchase #2 $126.39   6.458%   $134.5523   $134.55   $134.55   $134.60  
  Purchase #3 $10.44   3.609%   $10.8168   $10.82   $10.80   $10.80  
  Purchase #4 $73.47   10.535%   $81.2101   $81.21   $81.20   $81.20  
  Purchase #5 $206.73   8.261%   $223.808   $223.81   $223.80   $223.80  
  Purchase #6 $110.55   8.748%   $120.2209   $120.22   $120.20   $120.20  
  Purchase #7 $244.90   11.691%   $273.5313   $273.53   $273.55   $273.50  
  7 purchase totals = $830.82       $906.7038   $906.70   $906.65   $906.70