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 $88.67   8.551%   $96.2522   $96.25   $96.25   $96.30  
  Purchase #2 $74.30   5.858%   $78.6525   $78.65   $78.65   $78.70  
  Purchase #3 $214.49   11.453%   $239.0555   $239.06   $239.05   $239.10  
  Purchase #4 $143.78   8.774%   $156.3953   $156.40   $156.40   $156.40  
  Purchase #5 $236.48   7.295%   $253.7312   $253.73   $253.75   $253.70  
  Purchase #6 $173.40   7.784%   $186.8975   $186.90   $186.90   $186.90  
  Purchase #7 $184.59   9.655%   $202.4122   $202.41   $202.40   $202.40  
  7 purchase totals = $1,115.71       $1,213.3964   $1,213.40   $1,213.40   $1,213.50