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 $214.84   5.193%   $225.9966   $226.00   $226.00   $226.00  
  Purchase #2 $221.37   11.602%   $247.0533   $247.05   $247.05   $247.10  
  Purchase #3 $194.98   3.480%   $201.7653   $201.77   $201.75   $201.80  
  Purchase #4 $60.53   12.345%   $68.0024   $68.00   $68.00   $68.00  
  Purchase #5 $108.74   5.186%   $114.3793   $114.38   $114.40   $114.40  
  Purchase #6 $236.37   5.281%   $248.8527   $248.85   $248.85   $248.90  
  Purchase #7 $231.89   3.557%   $240.1383   $240.14   $240.15   $240.10  
  7 purchase totals = $1,268.72       $1,346.1879   $1,346.19   $1,346.20   $1,346.30