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 $214.35   4.642%   $224.3001   $224.30   $224.30   $224.30  
  Purchase #2 $242.45   9.778%   $266.1568   $266.16   $266.15   $266.20  
  Purchase #3 $45.70   6.629%   $48.7295   $48.73   $48.75   $48.70  
  Purchase #4 $229.62   3.460%   $237.5649   $237.56   $237.55   $237.60  
  Purchase #5 $174.30   8.570%   $189.2375   $189.24   $189.25   $189.20  
  Purchase #6 $199.49   8.123%   $215.6946   $215.69   $215.70   $215.70  
  Purchase #7 $211.61   8.568%   $229.7407   $229.74   $229.75   $229.70  
  7 purchase totals = $1,317.52       $1,411.4241   $1,411.42   $1,411.45   $1,411.40