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 $183.78   5.327%   $193.57   $193.57   $193.55   $193.60  
  Purchase #2 $209.37   12.475%   $235.4889   $235.49   $235.50   $235.50  
  Purchase #3 $68.55   7.615%   $73.7701   $73.77   $73.75   $73.80  
  Purchase #4 $110.88   4.105%   $115.4316   $115.43   $115.45   $115.40  
  Purchase #5 $110.61   3.609%   $114.6019   $114.60   $114.60   $114.60  
  Purchase #6 $87.88   8.138%   $95.0317   $95.03   $95.05   $95.00  
  Purchase #7 $213.29   5.214%   $224.4109   $224.41   $224.40   $224.40  
  7 purchase totals = $984.36       $1,052.3051   $1,052.30   $1,052.30   $1,052.30