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 $68.81   8.496%   $74.6561   $74.66   $74.65   $74.70  
  Purchase #2 $194.31   12.684%   $218.9563   $218.96   $218.95   $219.00  
  Purchase #3 $104.71   4.736%   $109.6691   $109.67   $109.65   $109.70  
  Purchase #4 $162.83   9.624%   $178.5008   $178.50   $178.50   $178.50  
  Purchase #5 $213.68   6.223%   $226.9773   $226.98   $227.00   $227.00  
  Purchase #6 $114.92   10.710%   $127.2279   $127.23   $127.25   $127.20  
  Purchase #7 $88.40   13.661%   $100.4763   $100.48   $100.50   $100.50  
  7 purchase totals = $947.66       $1,036.4638   $1,036.48   $1,036.50   $1,036.60