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 $59.84   5.349%   $63.0408   $63.04   $63.05   $63.00  
  Purchase #2 $164.35   7.222%   $176.2194   $176.22   $176.20   $176.20  
  Purchase #3 $38.34   5.226%   $40.3436   $40.34   $40.35   $40.30  
  Purchase #4 $226.31   7.300%   $242.8306   $242.83   $242.85   $242.80  
  Purchase #5 $168.91   10.502%   $186.6489   $186.65   $186.65   $186.60  
  Purchase #6 $48.87   12.852%   $55.1508   $55.15   $55.15   $55.20  
  Purchase #7 $248.71   6.839%   $265.7193   $265.72   $265.70   $265.70  
  7 purchase totals = $955.33       $1,029.9534   $1,029.95   $1,029.95   $1,029.80