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 $216.84   4.367%   $226.3094   $226.31   $226.30   $226.30  
  Purchase #2 $20.75   12.342%   $23.311   $23.31   $23.30   $23.30  
  Purchase #3 $44.84   10.288%   $49.4531   $49.45   $49.45   $49.50  
  Purchase #4 $174.99   11.433%   $194.9966   $195.00   $195.00   $195.00  
  Purchase #5 $192.99   7.833%   $208.1069   $208.11   $208.10   $208.10  
  Purchase #6 $215.80   3.783%   $223.9637   $223.96   $223.95   $224.00  
  Purchase #7 $213.35   11.405%   $237.6826   $237.68   $237.70   $237.70  
  7 purchase totals = $1,079.56       $1,163.8233   $1,163.82   $1,163.80   $1,163.90