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 $214.29   12.295%   $240.637   $240.64   $240.65   $240.60  
  Purchase #2 $187.28   5.171%   $196.9642   $196.96   $196.95   $197.00  
  Purchase #3 $9.65   6.813%   $10.3075   $10.31   $10.30   $10.30  
  Purchase #4 $215.26   9.699%   $236.1381   $236.14   $236.15   $236.10  
  Purchase #5 $121.66   3.301%   $125.676   $125.68   $125.70   $125.70  
  Purchase #6 $71.83   7.705%   $77.3645   $77.36   $77.35   $77.40  
  Purchase #7 $241.30   9.579%   $264.4141   $264.41   $264.40   $264.40  
  7 purchase totals = $1,061.27       $1,151.5014   $1,151.50   $1,151.50   $1,151.50