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 $218.61   3.712%   $226.7248   $226.72   $226.70   $226.70  
  Purchase #2 $207.41   4.327%   $216.3846   $216.38   $216.40   $216.40  
  Purchase #3 $43.64   3.665%   $45.2394   $45.24   $45.25   $45.20  
  Purchase #4 $88.64   4.570%   $92.6908   $92.69   $92.70   $92.70  
  Purchase #5 $244.83   7.195%   $262.4455   $262.45   $262.45   $262.40  
  Purchase #6 $163.35   5.321%   $172.0419   $172.04   $172.05   $172.00  
  Purchase #7 $78.80   10.208%   $86.8439   $86.84   $86.85   $86.80  
  7 purchase totals = $1,045.28       $1,102.3709   $1,102.36   $1,102.40   $1,102.20