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 $208.46   8.751%   $226.7023   $226.70   $226.70   $226.70  
  Purchase #2 $68.57   9.502%   $75.0855   $75.09   $75.10   $75.10  
  Purchase #3 $221.93   3.768%   $230.2923   $230.29   $230.30   $230.30  
  Purchase #4 $226.48   12.231%   $254.1808   $254.18   $254.20   $254.20  
  Purchase #5 $197.96   4.636%   $207.1374   $207.14   $207.15   $207.10  
  Purchase #6 $23.30   13.364%   $26.4138   $26.41   $26.40   $26.40  
  Purchase #7 $12.91   4.319%   $13.4676   $13.47   $13.45   $13.50  
  7 purchase totals = $959.61       $1,033.2797   $1,033.28   $1,033.30   $1,033.30