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 $216.31   10.760%   $239.585   $239.59   $239.60   $239.60  
  Purchase #2 $63.33   6.835%   $67.6586   $67.66   $67.65   $67.70  
  Purchase #3 $110.92   6.574%   $118.2119   $118.21   $118.20   $118.20  
  Purchase #4 $226.49   6.774%   $241.8324   $241.83   $241.85   $241.80  
  Purchase #5 $210.33   3.522%   $217.7378   $217.74   $217.75   $217.70  
  Purchase #6 $239.50   12.523%   $269.4926   $269.49   $269.50   $269.50  
  Purchase #7 $230.48   4.544%   $240.953   $240.95   $240.95   $241.00  
  7 purchase totals = $1,297.36       $1,395.4713   $1,395.47   $1,395.50   $1,395.50