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 $182.66   7.839%   $196.9787   $196.98   $197.00   $197.00  
  Purchase #2 $65.38   3.752%   $67.8331   $67.83   $67.85   $67.80  
  Purchase #3 $174.43   6.703%   $186.122   $186.12   $186.10   $186.10  
  Purchase #4 $44.54   11.207%   $49.5316   $49.53   $49.55   $49.50  
  Purchase #5 $192.34   11.585%   $214.6226   $214.62   $214.60   $214.60  
  Purchase #6 $125.34   11.605%   $139.8857   $139.89   $139.90   $139.90  
  Purchase #7 $202.70   10.104%   $223.1808   $223.18   $223.20   $223.20  
  7 purchase totals = $987.39       $1,078.1545   $1,078.15   $1,078.20   $1,078.10