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 $164.30   6.276%   $174.6115   $174.61   $174.60   $174.60  
  Purchase #2 $185.83   4.735%   $194.6291   $194.63   $194.65   $194.60  
  Purchase #3 $215.36   5.839%   $227.9349   $227.93   $227.95   $227.90  
  Purchase #4 $35.38   9.520%   $38.7482   $38.75   $38.75   $38.70  
  Purchase #5 $193.77   3.405%   $200.3679   $200.37   $200.35   $200.40  
  Purchase #6 $186.59   12.697%   $210.2813   $210.28   $210.30   $210.30  
  Purchase #7 $167.66   13.814%   $190.8206   $190.82   $190.80   $190.80  
  7 purchase totals = $1,148.89       $1,237.3935   $1,237.39   $1,237.40   $1,237.30