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 $238.41   12.843%   $269.029   $269.03   $269.05   $269.00  
  Purchase #2 $192.53   5.315%   $202.763   $202.76   $202.75   $202.80  
  Purchase #3 $76.94   3.388%   $79.5467   $79.55   $79.55   $79.50  
  Purchase #4 $77.99   5.539%   $82.3099   $82.31   $82.30   $82.30  
  Purchase #5 $222.60   13.765%   $253.2409   $253.24   $253.25   $253.20  
  Purchase #6 $120.40   9.470%   $131.8019   $131.80   $131.80   $131.80  
  Purchase #7 $101.69   3.871%   $105.6264   $105.63   $105.65   $105.60  
  7 purchase totals = $1,030.56       $1,124.3178   $1,124.32   $1,124.35   $1,124.20