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 $84.44   13.269%   $95.6443   $95.64   $95.65   $95.60  
  Purchase #2 $236.73   6.712%   $252.6193   $252.62   $252.60   $252.60  
  Purchase #3 $194.73   4.262%   $203.0294   $203.03   $203.05   $203.00  
  Purchase #4 $102.73   11.323%   $114.3621   $114.36   $114.35   $114.40  
  Purchase #5 $161.27   9.715%   $176.9374   $176.94   $176.95   $176.90  
  Purchase #6 $193.62   10.293%   $213.5493   $213.55   $213.55   $213.50  
  Purchase #7 $99.39   4.820%   $104.1806   $104.18   $104.20   $104.20  
  7 purchase totals = $1,072.91       $1,160.3224   $1,160.32   $1,160.35   $1,160.20