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 $192.28   8.300%   $208.2392   $208.24   $208.25   $208.20  
  Purchase #2 $114.46   10.808%   $126.8308   $126.83   $126.85   $126.80  
  Purchase #3 $173.73   11.194%   $193.1773   $193.18   $193.20   $193.20  
  Purchase #4 $58.43   5.119%   $61.421   $61.42   $61.40   $61.40  
  Purchase #5 $189.64   7.465%   $203.7966   $203.80   $203.80   $203.80  
  Purchase #6 $175.36   3.122%   $180.8347   $180.83   $180.85   $180.80  
  Purchase #7 $163.53   10.844%   $181.2632   $181.26   $181.25   $181.30  
  7 purchase totals = $1,067.43       $1,155.5628   $1,155.56   $1,155.60   $1,155.50