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 $181.77   13.168%   $205.7055   $205.71   $205.70   $205.70  
  Purchase #2 $187.91   11.132%   $208.8281   $208.83   $208.85   $208.80  
  Purchase #3 $47.45   6.281%   $50.4303   $50.43   $50.45   $50.40  
  Purchase #4 $194.68   3.702%   $201.8871   $201.89   $201.90   $201.90  
  Purchase #5 $17.27   5.523%   $18.2238   $18.22   $18.20   $18.20  
  Purchase #6 $194.92   11.621%   $217.5717   $217.57   $217.55   $217.60  
  Purchase #7 $102.47   11.422%   $114.1741   $114.17   $114.15   $114.20  
  7 purchase totals = $926.47       $1,016.8206   $1,016.82   $1,016.80   $1,016.80