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 $182.49   5.521%   $192.5653   $192.57   $192.55   $192.60  
  Purchase #2 $206.32   8.690%   $224.2492   $224.25   $224.25   $224.20  
  Purchase #3 $70.26   7.447%   $75.4923   $75.49   $75.50   $75.50  
  Purchase #4 $209.84   10.374%   $231.6088   $231.61   $231.60   $231.60  
  Purchase #5 $49.53   9.578%   $54.274   $54.27   $54.25   $54.30  
  Purchase #6 $126.35   4.252%   $131.7224   $131.72   $131.70   $131.70  
  Purchase #7 $186.28   6.504%   $198.3957   $198.40   $198.40   $198.40  
  7 purchase totals = $1,031.07       $1,108.3077   $1,108.31   $1,108.25   $1,108.30