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 $240.96   10.757%   $266.8801   $266.88   $266.90   $266.90  
  Purchase #2 $86.59   9.816%   $95.0897   $95.09   $95.10   $95.10  
  Purchase #3 $53.25   10.364%   $58.7688   $58.77   $58.75   $58.80  
  Purchase #4 $175.61   11.673%   $196.109   $196.11   $196.10   $196.10  
  Purchase #5 $214.34   5.439%   $225.998   $226.00   $226.00   $226.00  
  Purchase #6 $38.26   4.685%   $40.0525   $40.05   $40.05   $40.10  
  Purchase #7 $166.67   8.312%   $180.5236   $180.52   $180.50   $180.50  
  7 purchase totals = $975.68       $1,063.4217   $1,063.42   $1,063.40   $1,063.50