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 $32.61   6.322%   $34.6716   $34.67   $34.65   $34.70  
  Purchase #2 $147.56   11.487%   $164.5102   $164.51   $164.50   $164.50  
  Purchase #3 $36.40   11.716%   $40.6646   $40.66   $40.65   $40.70  
  Purchase #4 $211.48   8.751%   $229.9866   $229.99   $230.00   $230.00  
  Purchase #5 $174.34   13.542%   $197.9491   $197.95   $197.95   $197.90  
  Purchase #6 $187.43   7.346%   $201.1986   $201.20   $201.20   $201.20  
  Purchase #7 $176.29   12.612%   $198.5237   $198.52   $198.50   $198.50  
  7 purchase totals = $966.11       $1,067.5044   $1,067.50   $1,067.45   $1,067.50