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 $85.71   8.151%   $92.6962   $92.70   $92.70   $92.70  
  Purchase #2 $11.53   7.506%   $12.3954   $12.40   $12.40   $12.40  
  Purchase #3 $207.98   8.351%   $225.3484   $225.35   $225.35   $225.30  
  Purchase #4 $193.91   3.752%   $201.1855   $201.19   $201.20   $201.20  
  Purchase #5 $130.44   12.830%   $147.1755   $147.18   $147.20   $147.20  
  Purchase #6 $108.61   3.688%   $112.6155   $112.62   $112.60   $112.60  
  Purchase #7 $167.28   3.750%   $173.553   $173.55   $173.55   $173.60  
  7 purchase totals = $905.46       $964.9695   $964.99   $965.00   $965.00