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 $174.26   11.187%   $193.7545   $193.75   $193.75   $193.80  
  Purchase #2 $112.80   11.307%   $125.5543   $125.55   $125.55   $125.60  
  Purchase #3 $59.71   13.861%   $67.9864   $67.99   $68.00   $68.00  
  Purchase #4 $26.60   7.114%   $28.4923   $28.49   $28.50   $28.50  
  Purchase #5 $242.77   3.196%   $250.5289   $250.53   $250.55   $250.50  
  Purchase #6 $198.74   4.608%   $207.8979   $207.90   $207.90   $207.90  
  Purchase #7 $102.91   10.544%   $113.7608   $113.76   $113.75   $113.80  
  7 purchase totals = $917.79       $987.9751   $987.97   $988.00   $988.10