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 $156.80   6.624%   $167.1864   $167.19   $167.20   $167.20  
  Purchase #2 $195.96   8.336%   $212.2952   $212.30   $212.30   $212.30  
  Purchase #3 $202.56   12.158%   $227.1872   $227.19   $227.20   $227.20  
  Purchase #4 $214.89   8.768%   $233.7316   $233.73   $233.75   $233.70  
  Purchase #5 $62.96   11.159%   $69.9857   $69.99   $70.00   $70.00  
  Purchase #6 $196.55   10.724%   $217.628   $217.63   $217.65   $217.60  
  Purchase #7 $81.51   13.518%   $92.5285   $92.53   $92.55   $92.50  
  7 purchase totals = $1,111.23       $1,220.5426   $1,220.56   $1,220.65   $1,220.50