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 $188.34   13.712%   $214.1652   $214.17   $214.15   $214.20  
  Purchase #2 $212.38   13.543%   $241.1426   $241.14   $241.15   $241.10  
  Purchase #3 $232.65   4.564%   $243.2681   $243.27   $243.25   $243.30  
  Purchase #4 $183.56   10.817%   $203.4157   $203.42   $203.40   $203.40  
  Purchase #5 $50.58   13.853%   $57.5868   $57.59   $57.60   $57.60  
  Purchase #6 $248.43   5.505%   $262.1061   $262.11   $262.10   $262.10  
  Purchase #7 $216.45   13.555%   $245.7898   $245.79   $245.80   $245.80  
  7 purchase totals = $1,332.39       $1,467.4743   $1,467.49   $1,467.45   $1,467.50