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 $216.98   4.358%   $226.436   $226.44   $226.45   $226.40  
  Purchase #2 $112.42   5.537%   $118.6447   $118.64   $118.65   $118.60  
  Purchase #3 $116.76   7.670%   $125.7155   $125.72   $125.70   $125.70  
  Purchase #4 $176.96   5.708%   $187.0609   $187.06   $187.05   $187.10  
  Purchase #5 $218.65   13.488%   $248.1415   $248.14   $248.15   $248.10  
  Purchase #6 $24.74   10.566%   $27.354   $27.35   $27.35   $27.40  
  Purchase #7 $170.34   12.786%   $192.1197   $192.12   $192.10   $192.10  
  7 purchase totals = $1,036.85       $1,125.4723   $1,125.47   $1,125.45   $1,125.40