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 $60.46   11.718%   $67.5447   $67.54   $67.55   $67.50  
  Purchase #2 $216.89   12.314%   $243.5978   $243.60   $243.60   $243.60  
  Purchase #3 $57.44   12.142%   $64.4144   $64.41   $64.40   $64.40  
  Purchase #4 $238.49   5.737%   $252.1722   $252.17   $252.15   $252.20  
  Purchase #5 $211.83   5.634%   $223.7645   $223.76   $223.75   $223.80  
  Purchase #6 $8.34   3.837%   $8.66   $8.66   $8.65   $8.70  
  Purchase #7 $151.47   11.517%   $168.9148   $168.91   $168.90   $168.90  
  7 purchase totals = $944.92       $1,029.0684   $1,029.05   $1,029.00   $1,029.10