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 $126.86   11.693%   $141.6937   $141.69   $141.70   $141.70  
  Purchase #2 $86.39   12.666%   $97.3322   $97.33   $97.35   $97.30  
  Purchase #3 $193.69   11.565%   $216.0902   $216.09   $216.10   $216.10  
  Purchase #4 $196.56   11.233%   $218.6396   $218.64   $218.65   $218.60  
  Purchase #5 $149.53   4.821%   $156.7388   $156.74   $156.75   $156.70  
  Purchase #6 $196.41   6.805%   $209.7757   $209.78   $209.80   $209.80  
  Purchase #7 $105.74   8.359%   $114.5788   $114.58   $114.60   $114.60  
  7 purchase totals = $1,055.18       $1,154.8490   $1,154.85   $1,154.95   $1,154.80