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 $177.97   9.547%   $194.9608   $194.96   $194.95   $195.00  
  Purchase #2 $61.80   9.408%   $67.6141   $67.61   $67.60   $67.60  
  Purchase #3 $113.55   9.619%   $124.4724   $124.47   $124.45   $124.50  
  Purchase #4 $208.95   11.136%   $232.2187   $232.22   $232.20   $232.20  
  Purchase #5 $201.35   13.464%   $228.4598   $228.46   $228.45   $228.50  
  Purchase #6 $108.54   5.311%   $114.3046   $114.30   $114.30   $114.30  
  Purchase #7 $44.63   11.696%   $49.8499   $49.85   $49.85   $49.80  
  7 purchase totals = $916.79       $1,011.8803   $1,011.87   $1,011.80   $1,011.90