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 $174.99   10.120%   $192.699   $192.70   $192.70   $192.70  
  Purchase #2 $192.48   6.613%   $205.2087   $205.21   $205.20   $205.20  
  Purchase #3 $20.73   8.470%   $22.4858   $22.49   $22.50   $22.50  
  Purchase #4 $240.61   12.797%   $271.4009   $271.40   $271.40   $271.40  
  Purchase #5 $114.70   3.796%   $119.054   $119.05   $119.05   $119.10  
  Purchase #6 $197.76   8.366%   $214.3046   $214.30   $214.30   $214.30  
  Purchase #7 $199.84   4.547%   $208.9267   $208.93   $208.95   $208.90  
  7 purchase totals = $1,141.11       $1,234.0797   $1,234.08   $1,234.10   $1,234.10