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 $120.42   5.266%   $126.7613   $126.76   $126.75   $126.80  
  Purchase #2 $11.45   10.393%   $12.64   $12.64   $12.65   $12.60  
  Purchase #3 $184.71   6.495%   $196.7069   $196.71   $196.70   $196.70  
  Purchase #4 $207.86   4.663%   $217.5525   $217.55   $217.55   $217.60  
  Purchase #5 $168.96   3.661%   $175.1456   $175.15   $175.15   $175.10  
  Purchase #6 $171.92   10.106%   $189.2942   $189.29   $189.30   $189.30  
  Purchase #7 $171.29   3.511%   $177.304   $177.30   $177.30   $177.30  
  7 purchase totals = $1,036.61       $1,095.4045   $1,095.40   $1,095.40   $1,095.40