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 $163.26   6.771%   $174.3143   $174.31   $174.30   $174.30  
  Purchase #2 $169.25   5.567%   $178.6721   $178.67   $178.65   $178.70  
  Purchase #3 $21.85   11.648%   $24.3951   $24.40   $24.40   $24.40  
  Purchase #4 $129.53   12.239%   $145.3832   $145.38   $145.40   $145.40  
  Purchase #5 $145.32   13.405%   $164.8001   $164.80   $164.80   $164.80  
  Purchase #6 $194.81   3.204%   $201.0517   $201.05   $201.05   $201.10  
  Purchase #7 $205.65   10.862%   $227.9877   $227.99   $228.00   $228.00  
  7 purchase totals = $1,029.67       $1,116.6042   $1,116.60   $1,116.60   $1,116.70