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 $176.51   11.144%   $196.1803   $196.18   $196.20   $196.20  
  Purchase #2 $154.31   5.741%   $163.1689   $163.17   $163.15   $163.20  
  Purchase #3 $212.98   6.383%   $226.5745   $226.57   $226.55   $226.60  
  Purchase #4 $56.77   8.587%   $61.6448   $61.64   $61.65   $61.60  
  Purchase #5 $159.83   13.721%   $181.7603   $181.76   $181.75   $181.80  
  Purchase #6 $218.90   8.337%   $237.1497   $237.15   $237.15   $237.10  
  Purchase #7 $175.59   11.612%   $195.9795   $195.98   $196.00   $196.00  
  7 purchase totals = $1,154.89       $1,262.4580   $1,262.45   $1,262.45   $1,262.50