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 $58.30   7.608%   $62.7355   $62.74   $62.75   $62.70  
  Purchase #2 $208.80   11.685%   $233.1983   $233.20   $233.20   $233.20  
  Purchase #3 $225.67   11.410%   $251.4189   $251.42   $251.40   $251.40  
  Purchase #4 $71.71   11.538%   $79.9839   $79.98   $80.00   $80.00  
  Purchase #5 $29.31   4.754%   $30.7034   $30.70   $30.70   $30.70  
  Purchase #6 $207.31   5.370%   $218.4425   $218.44   $218.45   $218.40  
  Purchase #7 $114.31   4.326%   $119.2551   $119.26   $119.25   $119.30  
  7 purchase totals = $915.41       $995.7376   $995.74   $995.75   $995.70