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 $41.83   4.445%   $43.6893   $43.69   $43.70   $43.70  
  Purchase #2 $105.35   5.193%   $110.8208   $110.82   $110.80   $110.80  
  Purchase #3 $104.87   9.320%   $114.6439   $114.64   $114.65   $114.60  
  Purchase #4 $117.34   11.194%   $130.475   $130.48   $130.50   $130.50  
  Purchase #5 $184.29   12.862%   $207.9934   $207.99   $208.00   $208.00  
  Purchase #6 $245.62   12.747%   $276.9292   $276.93   $276.95   $276.90  
  Purchase #7 $157.85   5.294%   $166.2066   $166.21   $166.20   $166.20  
  7 purchase totals = $957.15       $1,050.7582   $1,050.76   $1,050.80   $1,050.70