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 $176.46   11.243%   $196.2994   $196.30   $196.30   $196.30  
  Purchase #2 $219.88   12.549%   $247.4727   $247.47   $247.45   $247.50  
  Purchase #3 $123.55   12.109%   $138.5107   $138.51   $138.50   $138.50  
  Purchase #4 $140.92   4.778%   $147.6532   $147.65   $147.65   $147.70  
  Purchase #5 $95.79   6.397%   $101.9177   $101.92   $101.90   $101.90  
  Purchase #6 $165.47   7.194%   $177.3739   $177.37   $177.35   $177.40  
  Purchase #7 $147.61   4.630%   $154.4443   $154.44   $154.45   $154.40  
  7 purchase totals = $1,069.68       $1,163.6719   $1,163.66   $1,163.60   $1,163.70