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 $208.84   13.430%   $236.8872   $236.89   $236.90   $236.90  
  Purchase #2 $228.97   8.325%   $248.0318   $248.03   $248.05   $248.00  
  Purchase #3 $172.96   6.606%   $184.3857   $184.39   $184.40   $184.40  
  Purchase #4 $145.67   7.361%   $156.3928   $156.39   $156.40   $156.40  
  Purchase #5 $152.71   5.223%   $160.686   $160.69   $160.70   $160.70  
  Purchase #6 $22.35   9.201%   $24.4064   $24.41   $24.40   $24.40  
  Purchase #7 $35.57   4.625%   $37.2151   $37.22   $37.20   $37.20  
  7 purchase totals = $967.07       $1,048.0050   $1,048.02   $1,048.05   $1,048.00