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 $215.64   10.302%   $237.8552   $237.86   $237.85   $237.90  
  Purchase #2 $59.34   13.633%   $67.4298   $67.43   $67.45   $67.40  
  Purchase #3 $70.81   12.270%   $79.4984   $79.50   $79.50   $79.50  
  Purchase #4 $195.69   5.123%   $205.7152   $205.72   $205.70   $205.70  
  Purchase #5 $212.84   6.250%   $226.1425   $226.14   $226.15   $226.10  
  Purchase #6 $97.70   9.357%   $106.8418   $106.84   $106.85   $106.80  
  Purchase #7 $234.54   11.793%   $262.1993   $262.20   $262.20   $262.20  
  7 purchase totals = $1,086.56       $1,185.6822   $1,185.69   $1,185.70   $1,185.60