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 $208.83   13.804%   $237.6569   $237.66   $237.65   $237.70  
  Purchase #2 $5.56   3.307%   $5.7439   $5.74   $5.75   $5.70  
  Purchase #3 $92.30   12.312%   $103.664   $103.66   $103.65   $103.70  
  Purchase #4 $192.80   4.366%   $201.2176   $201.22   $201.20   $201.20  
  Purchase #5 $204.32   11.674%   $228.1723   $228.17   $228.15   $228.20  
  Purchase #6 $217.77   10.486%   $240.6054   $240.61   $240.60   $240.60  
  Purchase #7 $23.29   12.338%   $26.1635   $26.16   $26.15   $26.20  
  7 purchase totals = $944.87       $1,043.2236   $1,043.22   $1,043.15   $1,043.30