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 $182.80   11.396%   $203.6319   $203.63   $203.65   $203.60  
  Purchase #2 $12.91   10.137%   $14.2187   $14.22   $14.20   $14.20  
  Purchase #3 $60.95   10.852%   $67.5643   $67.56   $67.55   $67.60  
  Purchase #4 $245.67   10.357%   $271.114   $271.11   $271.10   $271.10  
  Purchase #5 $114.83   11.149%   $127.6324   $127.63   $127.65   $127.60  
  Purchase #6 $182.39   12.252%   $204.7364   $204.74   $204.75   $204.70  
  Purchase #7 $191.78   12.734%   $216.2013   $216.20   $216.20   $216.20  
  7 purchase totals = $991.33       $1,105.0990   $1,105.09   $1,105.10   $1,105.00