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 $34.71   4.459%   $36.2577   $36.26   $36.25   $36.30  
  Purchase #2 $184.34   6.398%   $196.1341   $196.13   $196.15   $196.10  
  Purchase #3 $53.26   10.462%   $58.8321   $58.83   $58.85   $58.80  
  Purchase #4 $247.45   6.186%   $262.7573   $262.76   $262.75   $262.80  
  Purchase #5 $208.54   10.605%   $230.6557   $230.66   $230.65   $230.70  
  Purchase #6 $52.43   7.650%   $56.4409   $56.44   $56.45   $56.40  
  Purchase #7 $150.27   11.249%   $167.1739   $167.17   $167.15   $167.20  
  7 purchase totals = $931.00       $1,008.2517   $1,008.25   $1,008.25   $1,008.30