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 $126.65   13.684%   $143.9808   $143.98   $144.00   $144.00  
  Purchase #2 $231.35   13.346%   $262.226   $262.23   $262.25   $262.20  
  Purchase #3 $73.72   5.371%   $77.6795   $77.68   $77.70   $77.70  
  Purchase #4 $32.52   11.779%   $36.3505   $36.35   $36.35   $36.40  
  Purchase #5 $168.67   11.146%   $187.47   $187.47   $187.45   $187.50  
  Purchase #6 $137.96   7.832%   $148.765   $148.77   $148.75   $148.80  
  Purchase #7 $163.85   7.214%   $175.6701   $175.67   $175.65   $175.70  
  7 purchase totals = $934.72       $1,032.1419   $1,032.15   $1,032.15   $1,032.30