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 $88.84   7.463%   $95.4701   $95.47   $95.45   $95.50  
  Purchase #2 $233.64   3.396%   $241.5744   $241.57   $241.55   $241.60  
  Purchase #3 $136.49   3.867%   $141.7681   $141.77   $141.75   $141.80  
  Purchase #4 $144.88   8.580%   $157.3107   $157.31   $157.30   $157.30  
  Purchase #5 $210.99   10.598%   $233.3507   $233.35   $233.35   $233.40  
  Purchase #6 $215.99   8.849%   $235.103   $235.10   $235.10   $235.10  
  Purchase #7 $208.91   7.458%   $224.4905   $224.49   $224.50   $224.50  
  7 purchase totals = $1,239.74       $1,329.0675   $1,329.06   $1,329.00   $1,329.20