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 $56.54   11.834%   $63.2309   $63.23   $63.25   $63.20  
  Purchase #2 $179.39   12.535%   $201.8765   $201.88   $201.90   $201.90  
  Purchase #3 $79.95   5.594%   $84.4224   $84.42   $84.40   $84.40  
  Purchase #4 $219.26   9.679%   $240.4822   $240.48   $240.50   $240.50  
  Purchase #5 $214.29   5.712%   $226.5302   $226.53   $226.55   $226.50  
  Purchase #6 $180.50   10.403%   $199.2774   $199.28   $199.30   $199.30  
  Purchase #7 $173.72   10.837%   $192.546   $192.55   $192.55   $192.50  
  7 purchase totals = $1,103.65       $1,208.3656   $1,208.37   $1,208.45   $1,208.30