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 $195.48   11.335%   $217.6377   $217.64   $217.65   $217.60  
  Purchase #2 $247.35   5.819%   $261.7433   $261.74   $261.75   $261.70  
  Purchase #3 $162.45   8.703%   $176.588   $176.59   $176.60   $176.60  
  Purchase #4 $31.27   3.624%   $32.4032   $32.40   $32.40   $32.40  
  Purchase #5 $190.30   4.490%   $198.8445   $198.84   $198.85   $198.80  
  Purchase #6 $60.67   4.494%   $63.3965   $63.40   $63.40   $63.40  
  Purchase #7 $242.26   10.870%   $268.5937   $268.59   $268.60   $268.60  
  7 purchase totals = $1,129.78       $1,219.2069   $1,219.20   $1,219.25   $1,219.10