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 $206.87   9.548%   $226.6219   $226.62   $226.60   $226.60  
  Purchase #2 $32.45   11.866%   $36.3005   $36.30   $36.30   $36.30  
  Purchase #3 $36.99   4.486%   $38.6494   $38.65   $38.65   $38.60  
  Purchase #4 $227.85   5.619%   $240.6529   $240.65   $240.65   $240.70  
  Purchase #5 $225.94   4.267%   $235.5809   $235.58   $235.60   $235.60  
  Purchase #6 $242.27   7.367%   $260.118   $260.12   $260.10   $260.10  
  Purchase #7 $144.36   9.411%   $157.9457   $157.95   $157.95   $157.90  
  7 purchase totals = $1,116.73       $1,195.8693   $1,195.87   $1,195.85   $1,195.80