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 $227.50   11.199%   $252.9777   $252.98   $253.00   $253.00  
  Purchase #2 $158.43   5.590%   $167.2862   $167.29   $167.30   $167.30  
  Purchase #3 $63.70   13.461%   $72.2747   $72.27   $72.25   $72.30  
  Purchase #4 $110.94   9.602%   $121.5925   $121.59   $121.60   $121.60  
  Purchase #5 $119.45   4.160%   $124.4191   $124.42   $124.40   $124.40  
  Purchase #6 $105.79   8.256%   $114.524   $114.52   $114.50   $114.50  
  Purchase #7 $200.71   6.872%   $214.5028   $214.50   $214.50   $214.50  
  7 purchase totals = $986.52       $1,067.5770   $1,067.57   $1,067.55   $1,067.60