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 $215.58   7.620%   $232.0072   $232.01   $232.00   $232.00  
  Purchase #2 $163.59   11.836%   $182.9525   $182.95   $182.95   $183.00  
  Purchase #3 $151.43   4.295%   $157.9339   $157.93   $157.95   $157.90  
  Purchase #4 $156.48   4.537%   $163.5795   $163.58   $163.60   $163.60  
  Purchase #5 $184.57   4.725%   $193.2909   $193.29   $193.30   $193.30  
  Purchase #6 $43.42   12.293%   $48.7576   $48.76   $48.75   $48.80  
  Purchase #7 $59.62   6.189%   $63.3099   $63.31   $63.30   $63.30  
  7 purchase totals = $974.69       $1,041.8315   $1,041.83   $1,041.85   $1,041.90