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 $77.83   10.503%   $86.0045   $86.00   $86.00   $86.00  
  Purchase #2 $116.92   8.449%   $126.7986   $126.80   $126.80   $126.80  
  Purchase #3 $240.31   13.483%   $272.711   $272.71   $272.70   $272.70  
  Purchase #4 $243.99   3.223%   $251.8538   $251.85   $251.85   $251.90  
  Purchase #5 $89.92   7.151%   $96.3502   $96.35   $96.35   $96.40  
  Purchase #6 $199.25   10.120%   $219.4141   $219.41   $219.40   $219.40  
  Purchase #7 $146.41   11.710%   $163.5546   $163.55   $163.55   $163.60  
  7 purchase totals = $1,114.63       $1,216.6868   $1,216.67   $1,216.65   $1,216.80