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 $233.67   3.152%   $241.0353   $241.04   $241.05   $241.00  
  Purchase #2 $47.94   8.775%   $52.1467   $52.15   $52.15   $52.10  
  Purchase #3 $112.67   7.147%   $120.7225   $120.72   $120.70   $120.70  
  Purchase #4 $218.54   5.470%   $230.4941   $230.49   $230.50   $230.50  
  Purchase #5 $135.39   6.856%   $144.6723   $144.67   $144.65   $144.70  
  Purchase #6 $134.25   8.693%   $145.9204   $145.92   $145.90   $145.90  
  Purchase #7 $174.68   7.302%   $187.4351   $187.44   $187.45   $187.40  
  7 purchase totals = $1,057.14       $1,122.4264   $1,122.43   $1,122.40   $1,122.30