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 $114.62   9.645%   $125.6751   $125.68   $125.70   $125.70  
  Purchase #2 $80.85   4.481%   $84.4729   $84.47   $84.45   $84.50  
  Purchase #3 $82.80   11.116%   $92.004   $92.00   $92.00   $92.00  
  Purchase #4 $50.77   6.335%   $53.9863   $53.99   $54.00   $54.00  
  Purchase #5 $205.51   3.496%   $212.6946   $212.69   $212.70   $212.70  
  Purchase #6 $186.83   6.277%   $198.5573   $198.56   $198.55   $198.60  
  Purchase #7 $60.69   10.865%   $67.284   $67.28   $67.30   $67.30  
  7 purchase totals = $782.07       $834.6742   $834.67   $834.70   $834.80