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 $177.48   11.141%   $197.253   $197.25   $197.25   $197.30  
  Purchase #2 $232.78   6.832%   $248.6835   $248.68   $248.70   $248.70  
  Purchase #3 $95.83   9.593%   $105.023   $105.02   $105.00   $105.00  
  Purchase #4 $155.51   4.116%   $161.9108   $161.91   $161.90   $161.90  
  Purchase #5 $178.88   10.662%   $197.9522   $197.95   $197.95   $198.00  
  Purchase #6 $54.91   3.811%   $57.0026   $57.00   $57.00   $57.00  
  Purchase #7 $60.89   12.538%   $68.5244   $68.52   $68.50   $68.50  
  7 purchase totals = $956.28       $1,036.3495   $1,036.33   $1,036.30   $1,036.40