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 $201.25   6.440%   $214.2105   $214.21   $214.20   $214.20  
  Purchase #2 $56.52   3.589%   $58.5485   $58.55   $58.55   $58.50  
  Purchase #3 $124.70   11.217%   $138.6876   $138.69   $138.70   $138.70  
  Purchase #4 $239.64   3.547%   $248.14   $248.14   $248.15   $248.10  
  Purchase #5 $240.88   5.247%   $253.519   $253.52   $253.50   $253.50  
  Purchase #6 $131.40   8.288%   $142.2904   $142.29   $142.30   $142.30  
  Purchase #7 $132.60   5.474%   $139.8585   $139.86   $139.85   $139.90  
  7 purchase totals = $1,126.99       $1,195.2545   $1,195.26   $1,195.25   $1,195.20