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 $191.34   11.295%   $212.9519   $212.95   $212.95   $213.00  
  Purchase #2 $193.87   11.253%   $215.6862   $215.69   $215.70   $215.70  
  Purchase #3 $76.88   5.630%   $81.2083   $81.21   $81.20   $81.20  
  Purchase #4 $93.62   13.425%   $106.1885   $106.19   $106.20   $106.20  
  Purchase #5 $204.95   6.220%   $217.6979   $217.70   $217.70   $217.70  
  Purchase #6 $120.69   5.411%   $127.2205   $127.22   $127.20   $127.20  
  Purchase #7 $247.35   7.376%   $265.5945   $265.59   $265.60   $265.60  
  7 purchase totals = $1,128.70       $1,226.5478   $1,226.55   $1,226.55   $1,226.60