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 $68.82   11.401%   $76.6662   $76.67   $76.65   $76.70  
  Purchase #2 $55.39   10.714%   $61.3245   $61.32   $61.30   $61.30  
  Purchase #3 $93.53   8.598%   $101.5717   $101.57   $101.55   $101.60  
  Purchase #4 $80.48   3.499%   $83.296   $83.30   $83.30   $83.30  
  Purchase #5 $124.95   8.595%   $135.6895   $135.69   $135.70   $135.70  
  Purchase #6 $187.41   10.469%   $207.03   $207.03   $207.05   $207.00  
  Purchase #7 $68.75   4.464%   $71.819   $71.82   $71.80   $71.80  
  7 purchase totals = $679.33       $737.3969   $737.40   $737.35   $737.40