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 $56.32   10.522%   $62.246   $62.25   $62.25   $62.20  
  Purchase #2 $122.26   9.301%   $133.6314   $133.63   $133.65   $133.60  
  Purchase #3 $107.52   5.592%   $113.5325   $113.53   $113.55   $113.50  
  Purchase #4 $193.97   10.868%   $215.0507   $215.05   $215.05   $215.10  
  Purchase #5 $204.51   9.312%   $223.554   $223.55   $223.55   $223.60  
  Purchase #6 $73.66   10.866%   $81.6639   $81.66   $81.65   $81.70  
  Purchase #7 $90.68   11.139%   $100.7808   $100.78   $100.80   $100.80  
  7 purchase totals = $848.92       $930.4593   $930.45   $930.50   $930.50