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 $46.73   4.811%   $48.9782   $48.98   $49.00   $49.00  
  Purchase #2 $13.26   7.483%   $14.2522   $14.25   $14.25   $14.30  
  Purchase #3 $168.69   3.460%   $174.5267   $174.53   $174.55   $174.50  
  Purchase #4 $55.73   7.799%   $60.0764   $60.08   $60.10   $60.10  
  Purchase #5 $63.88   13.755%   $72.6667   $72.67   $72.65   $72.70  
  Purchase #6 $188.39   4.469%   $196.8091   $196.81   $196.80   $196.80  
  Purchase #7 $161.61   4.770%   $169.3188   $169.32   $169.30   $169.30  
  7 purchase totals = $698.29       $736.6281   $736.64   $736.65   $736.70