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 $192.87   5.698%   $203.8597   $203.86   $203.85   $203.90  
  Purchase #2 $222.69   11.633%   $248.5955   $248.60   $248.60   $248.60  
  Purchase #3 $156.85   7.611%   $168.7879   $168.79   $168.80   $168.80  
  Purchase #4 $119.77   3.703%   $124.2051   $124.21   $124.20   $124.20  
  Purchase #5 $113.45   6.776%   $121.1374   $121.14   $121.15   $121.10  
  Purchase #6 $164.57   3.373%   $170.1209   $170.12   $170.10   $170.10  
  Purchase #7 $41.77   11.187%   $46.4428   $46.44   $46.45   $46.40  
  7 purchase totals = $1,011.97       $1,083.1493   $1,083.16   $1,083.15   $1,083.10