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 $243.46   7.385%   $261.4395   $261.44   $261.45   $261.40  
  Purchase #2 $115.50   4.794%   $121.0371   $121.04   $121.05   $121.00  
  Purchase #3 $47.69   13.133%   $53.9531   $53.95   $53.95   $54.00  
  Purchase #4 $177.68   7.688%   $191.34   $191.34   $191.35   $191.30  
  Purchase #5 $58.96   5.220%   $62.0377   $62.04   $62.05   $62.00  
  Purchase #6 $109.33   12.118%   $122.5786   $122.58   $122.60   $122.60  
  Purchase #7 $233.63   7.542%   $251.2504   $251.25   $251.25   $251.30  
  7 purchase totals = $986.25       $1,063.6364   $1,063.64   $1,063.70   $1,063.60