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 $160.51   8.407%   $174.0041   $174.00   $174.00   $174.00  
  Purchase #2 $246.44   8.622%   $267.6881   $267.69   $267.70   $267.70  
  Purchase #3 $223.31   13.240%   $252.8762   $252.88   $252.90   $252.90  
  Purchase #4 $185.87   9.233%   $203.0314   $203.03   $203.05   $203.00  
  Purchase #5 $231.72   9.250%   $253.1541   $253.15   $253.15   $253.20  
  Purchase #6 $248.65   7.491%   $267.2764   $267.28   $267.30   $267.30  
  Purchase #7 $177.88   10.185%   $195.9971   $196.00   $196.00   $196.00  
  7 purchase totals = $1,474.38       $1,614.0274   $1,614.03   $1,614.10   $1,614.10