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 $235.67   11.166%   $261.9849   $261.98   $262.00   $262.00  
  Purchase #2 $182.91   10.793%   $202.6515   $202.65   $202.65   $202.70  
  Purchase #3 $225.59   9.335%   $246.6488   $246.65   $246.65   $246.60  
  Purchase #4 $242.35   10.112%   $266.8564   $266.86   $266.85   $266.90  
  Purchase #5 $42.41   7.389%   $45.5437   $45.54   $45.55   $45.50  
  Purchase #6 $48.28   4.514%   $50.4594   $50.46   $50.45   $50.50  
  Purchase #7 $40.58   7.207%   $43.5046   $43.50   $43.50   $43.50  
  7 purchase totals = $1,017.79       $1,117.6493   $1,117.64   $1,117.65   $1,117.70