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 $201.59   5.857%   $213.3971   $213.40   $213.40   $213.40  
  Purchase #2 $78.64   7.824%   $84.7928   $84.79   $84.80   $84.80  
  Purchase #3 $246.60   11.141%   $274.0737   $274.07   $274.05   $274.10  
  Purchase #4 $169.51   3.436%   $175.3344   $175.33   $175.35   $175.30  
  Purchase #5 $49.71   12.606%   $55.9764   $55.98   $56.00   $56.00  
  Purchase #6 $194.93   13.509%   $221.2631   $221.26   $221.25   $221.30  
  Purchase #7 $32.26   8.824%   $35.1066   $35.11   $35.10   $35.10  
  7 purchase totals = $973.24       $1,059.9441   $1,059.94   $1,059.95   $1,060.00