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 $60.46   3.478%   $62.5628   $62.56   $62.55   $62.60  
  Purchase #2 $157.69   13.628%   $179.18   $179.18   $179.20   $179.20  
  Purchase #3 $82.80   10.194%   $91.2406   $91.24   $91.25   $91.20  
  Purchase #4 $64.84   12.751%   $73.1077   $73.11   $73.10   $73.10  
  Purchase #5 $70.80   9.216%   $77.3249   $77.32   $77.30   $77.30  
  Purchase #6 $14.36   8.535%   $15.5856   $15.59   $15.60   $15.60  
  Purchase #7 $57.81   5.151%   $60.7878   $60.79   $60.80   $60.80  
  7 purchase totals = $508.76       $559.7894   $559.79   $559.80   $559.80