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 $63.96   7.158%   $68.5383   $68.54   $68.55   $68.50  
  Purchase #2 $134.97   3.246%   $139.3511   $139.35   $139.35   $139.40  
  Purchase #3 $184.95   4.405%   $193.097   $193.10   $193.10   $193.10  
  Purchase #4 $197.33   10.167%   $217.3925   $217.39   $217.40   $217.40  
  Purchase #5 $89.93   5.325%   $94.7188   $94.72   $94.70   $94.70  
  Purchase #6 $114.58   10.755%   $126.9031   $126.90   $126.90   $126.90  
  Purchase #7 $226.88   3.528%   $234.8843   $234.88   $234.90   $234.90  
  7 purchase totals = $1,012.60       $1,074.8851   $1,074.88   $1,074.90   $1,074.90