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 $155.98   11.834%   $174.4387   $174.44   $174.45   $174.40  
  Purchase #2 $95.58   13.676%   $108.6515   $108.65   $108.65   $108.70  
  Purchase #3 $53.59   3.554%   $55.4946   $55.49   $55.50   $55.50  
  Purchase #4 $114.64   8.685%   $124.5965   $124.60   $124.60   $124.60  
  Purchase #5 $30.77   12.743%   $34.691   $34.69   $34.70   $34.70  
  Purchase #6 $235.89   8.577%   $256.1223   $256.12   $256.10   $256.10  
  Purchase #7 $182.69   6.381%   $194.3474   $194.35   $194.35   $194.30  
  7 purchase totals = $869.14       $948.3420   $948.34   $948.35   $948.30