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 $182.26   6.577%   $194.2472   $194.25   $194.25   $194.20  
  Purchase #2 $245.77   11.309%   $273.5641   $273.56   $273.55   $273.60  
  Purchase #3 $240.56   8.204%   $260.2955   $260.30   $260.30   $260.30  
  Purchase #4 $14.51   3.826%   $15.0652   $15.07   $15.05   $15.10  
  Purchase #5 $135.50   4.459%   $141.5419   $141.54   $141.55   $141.50  
  Purchase #6 $192.71   12.556%   $216.9067   $216.91   $216.90   $216.90  
  Purchase #7 $182.60   10.400%   $201.5904   $201.59   $201.60   $201.60  
  7 purchase totals = $1,193.91       $1,303.2110   $1,303.22   $1,303.20   $1,303.20