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 $181.67   7.641%   $195.5514   $195.55   $195.55   $195.60  
  Purchase #2 $93.83   5.152%   $98.6641   $98.66   $98.65   $98.70  
  Purchase #3 $195.86   12.422%   $220.1897   $220.19   $220.20   $220.20  
  Purchase #4 $79.46   3.554%   $82.284   $82.28   $82.30   $82.30  
  Purchase #5 $125.64   7.240%   $134.7363   $134.74   $134.75   $134.70  
  Purchase #6 $224.54   11.384%   $250.1016   $250.10   $250.10   $250.10  
  Purchase #7 $110.57   3.740%   $114.7053   $114.71   $114.70   $114.70  
  7 purchase totals = $1,011.57       $1,096.2324   $1,096.23   $1,096.25   $1,096.30