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 $126.26   11.710%   $141.045   $141.05   $141.05   $141.00  
  Purchase #2 $44.68   11.233%   $49.6989   $49.70   $49.70   $49.70  
  Purchase #3 $29.28   11.245%   $32.5725   $32.57   $32.55   $32.60  
  Purchase #4 $125.71   7.134%   $134.6782   $134.68   $134.70   $134.70  
  Purchase #5 $160.68   7.536%   $172.7888   $172.79   $172.80   $172.80  
  Purchase #6 $5.44   8.345%   $5.894   $5.89   $5.90   $5.90  
  Purchase #7 $207.53   9.218%   $226.6601   $226.66   $226.65   $226.70  
  7 purchase totals = $699.58       $763.3375   $763.34   $763.35   $763.40