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 $24.97   4.745%   $26.1548   $26.15   $26.15   $26.20  
  Purchase #2 $230.39   4.859%   $241.5847   $241.58   $241.60   $241.60  
  Purchase #3 $16.61   7.793%   $17.9044   $17.90   $17.90   $17.90  
  Purchase #4 $205.81   5.128%   $216.3639   $216.36   $216.35   $216.40  
  Purchase #5 $207.77   7.822%   $224.0218   $224.02   $224.00   $224.00  
  Purchase #6 $240.88   11.583%   $268.7811   $268.78   $268.80   $268.80  
  Purchase #7 $60.37   5.502%   $63.6916   $63.69   $63.70   $63.70  
  7 purchase totals = $986.80       $1,058.5023   $1,058.48   $1,058.50   $1,058.60