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 $201.25   3.377%   $208.0462   $208.05   $208.05   $208.00  
  Purchase #2 $190.52   8.538%   $206.7866   $206.79   $206.80   $206.80  
  Purchase #3 $10.40   11.785%   $11.6256   $11.63   $11.65   $11.60  
  Purchase #4 $147.43   6.693%   $157.2975   $157.30   $157.30   $157.30  
  Purchase #5 $155.44   5.827%   $164.4975   $164.50   $164.50   $164.50  
  Purchase #6 $249.75   7.532%   $268.5612   $268.56   $268.55   $268.60  
  Purchase #7 $89.29   5.256%   $93.9831   $93.98   $94.00   $94.00  
  7 purchase totals = $1,044.08       $1,110.7977   $1,110.81   $1,110.85   $1,110.80