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 $241.48   10.665%   $267.2338   $267.23   $267.25   $267.20  
  Purchase #2 $143.77   9.116%   $156.8761   $156.88   $156.90   $156.90  
  Purchase #3 $68.90   10.316%   $76.0077   $76.01   $76.00   $76.00  
  Purchase #4 $152.70   11.603%   $170.4178   $170.42   $170.40   $170.40  
  Purchase #5 $187.60   4.488%   $196.0195   $196.02   $196.00   $196.00  
  Purchase #6 $220.68   8.405%   $239.2282   $239.23   $239.25   $239.20  
  Purchase #7 $87.79   9.796%   $96.3899   $96.39   $96.40   $96.40  
  7 purchase totals = $1,102.92       $1,202.1730   $1,202.18   $1,202.20   $1,202.10