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 $110.96   7.266%   $119.0224   $119.02   $119.00   $119.00  
  Purchase #2 $196.61   6.710%   $209.8025   $209.80   $209.80   $209.80  
  Purchase #3 $53.81   13.739%   $61.203   $61.20   $61.20   $61.20  
  Purchase #4 $158.26   4.164%   $164.8499   $164.85   $164.85   $164.80  
  Purchase #5 $181.88   7.296%   $195.15   $195.15   $195.15   $195.20  
  Purchase #6 $27.40   3.575%   $28.3796   $28.38   $28.40   $28.40  
  Purchase #7 $71.58   5.847%   $75.7653   $75.77   $75.75   $75.80  
  7 purchase totals = $800.50       $854.1727   $854.17   $854.15   $854.20