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 $43.94   9.454%   $48.0941   $48.09   $48.10   $48.10  
  Purchase #2 $172.85   11.441%   $192.6258   $192.63   $192.65   $192.60  
  Purchase #3 $74.39   10.135%   $81.9294   $81.93   $81.95   $81.90  
  Purchase #4 $193.64   7.361%   $207.8938   $207.89   $207.90   $207.90  
  Purchase #5 $226.65   9.793%   $248.8458   $248.85   $248.85   $248.80  
  Purchase #6 $216.93   3.270%   $224.0236   $224.02   $224.00   $224.00  
  Purchase #7 $233.75   7.662%   $251.6599   $251.66   $251.65   $251.70  
  7 purchase totals = $1,162.15       $1,255.0724   $1,255.07   $1,255.10   $1,255.00