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 $119.76   6.624%   $127.6929   $127.69   $127.70   $127.70  
  Purchase #2 $29.75   12.190%   $33.3765   $33.38   $33.40   $33.40  
  Purchase #3 $198.89   10.534%   $219.8411   $219.84   $219.85   $219.80  
  Purchase #4 $156.55   6.292%   $166.4001   $166.40   $166.40   $166.40  
  Purchase #5 $168.67   4.862%   $176.8707   $176.87   $176.85   $176.90  
  Purchase #6 $230.44   5.729%   $243.6419   $243.64   $243.65   $243.60  
  Purchase #7 $226.93   4.523%   $237.194   $237.19   $237.20   $237.20  
  7 purchase totals = $1,130.99       $1,205.0172   $1,205.01   $1,205.05   $1,205.00