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 $217.58   6.701%   $232.16   $232.16   $232.15   $232.20  
  Purchase #2 $248.32   3.117%   $256.0601   $256.06   $256.05   $256.10  
  Purchase #3 $48.93   10.545%   $54.0897   $54.09   $54.10   $54.10  
  Purchase #4 $153.73   6.770%   $164.1375   $164.14   $164.15   $164.10  
  Purchase #5 $212.48   9.557%   $232.7867   $232.79   $232.80   $232.80  
  Purchase #6 $65.38   4.569%   $68.3672   $68.37   $68.35   $68.40  
  Purchase #7 $180.26   4.683%   $188.7016   $188.70   $188.70   $188.70  
  7 purchase totals = $1,126.68       $1,196.3028   $1,196.31   $1,196.30   $1,196.40