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 $46.44   13.570%   $52.7419   $52.74   $52.75   $52.70  
  Purchase #2 $239.58   10.461%   $264.6425   $264.64   $264.65   $264.60  
  Purchase #3 $184.30   4.394%   $192.3981   $192.40   $192.40   $192.40  
  Purchase #4 $87.91   5.623%   $92.8532   $92.85   $92.85   $92.90  
  Purchase #5 $176.99   3.186%   $182.6289   $182.63   $182.65   $182.60  
  Purchase #6 $147.46   4.472%   $154.0544   $154.05   $154.05   $154.10  
  Purchase #7 $191.38   12.292%   $214.9044   $214.90   $214.90   $214.90  
  7 purchase totals = $1,074.06       $1,154.2234   $1,154.21   $1,154.25   $1,154.20