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 $70.69   7.854%   $76.242   $76.24   $76.25   $76.20  
  Purchase #2 $177.34   8.543%   $192.4902   $192.49   $192.50   $192.50  
  Purchase #3 $207.69   7.746%   $223.7777   $223.78   $223.80   $223.80  
  Purchase #4 $234.57   9.724%   $257.3796   $257.38   $257.40   $257.40  
  Purchase #5 $200.53   3.578%   $207.705   $207.71   $207.70   $207.70  
  Purchase #6 $37.87   4.817%   $39.6942   $39.69   $39.70   $39.70  
  Purchase #7 $142.53   9.598%   $156.21   $156.21   $156.20   $156.20  
  7 purchase totals = $1,071.22       $1,153.4987   $1,153.50   $1,153.55   $1,153.50