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 $175.43   11.770%   $196.0781   $196.08   $196.10   $196.10  
  Purchase #2 $31.72   7.338%   $34.0476   $34.05   $34.05   $34.00  
  Purchase #3 $34.74   8.290%   $37.6199   $37.62   $37.60   $37.60  
  Purchase #4 $241.81   7.215%   $259.2566   $259.26   $259.25   $259.30  
  Purchase #5 $42.46   10.695%   $47.0011   $47.00   $47.00   $47.00  
  Purchase #6 $112.47   11.491%   $125.3939   $125.39   $125.40   $125.40  
  Purchase #7 $62.36   7.688%   $67.1542   $67.15   $67.15   $67.20  
  7 purchase totals = $700.99       $766.5514   $766.55   $766.55   $766.60