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 $214.73   12.119%   $240.7531   $240.75   $240.75   $240.80  
  Purchase #2 $65.53   7.718%   $70.5876   $70.59   $70.60   $70.60  
  Purchase #3 $159.61   10.272%   $176.0051   $176.01   $176.00   $176.00  
  Purchase #4 $128.95   8.451%   $139.8476   $139.85   $139.85   $139.80  
  Purchase #5 $96.79   10.258%   $106.7187   $106.72   $106.70   $106.70  
  Purchase #6 $192.65   10.305%   $212.5026   $212.50   $212.50   $212.50  
  Purchase #7 $219.51   13.246%   $248.5863   $248.59   $248.60   $248.60  
  7 purchase totals = $1,077.77       $1,195.0010   $1,195.01   $1,195.00   $1,195.00