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 $114.84   4.114%   $119.5645   $119.56   $119.55   $119.60  
  Purchase #2 $249.43   13.325%   $282.6665   $282.67   $282.65   $282.70  
  Purchase #3 $131.98   8.203%   $142.8063   $142.81   $142.80   $142.80  
  Purchase #4 $107.77   11.248%   $119.892   $119.89   $119.90   $119.90  
  Purchase #5 $160.93   4.815%   $168.6788   $168.68   $168.70   $168.70  
  Purchase #6 $246.50   7.284%   $264.4551   $264.46   $264.45   $264.50  
  Purchase #7 $16.26   4.116%   $16.9293   $16.93   $16.95   $16.90  
  7 purchase totals = $1,027.71       $1,114.9925   $1,115.00   $1,115.00   $1,115.10