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 $114.33   9.862%   $125.6052   $125.61   $125.60   $125.60  
  Purchase #2 $182.48   11.461%   $203.394   $203.39   $203.40   $203.40  
  Purchase #3 $248.86   6.458%   $264.9314   $264.93   $264.95   $264.90  
  Purchase #4 $151.74   13.746%   $172.5982   $172.60   $172.60   $172.60  
  Purchase #5 $227.43   8.116%   $245.8882   $245.89   $245.90   $245.90  
  Purchase #6 $160.39   12.255%   $180.0458   $180.05   $180.05   $180.00  
  Purchase #7 $101.32   7.799%   $109.2219   $109.22   $109.20   $109.20  
  7 purchase totals = $1,186.55       $1,301.6847   $1,301.69   $1,301.70   $1,301.60