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 $245.75   7.446%   $264.0485   $264.05   $264.05   $264.00  
  Purchase #2 $171.94   8.210%   $186.0563   $186.06   $186.05   $186.10  
  Purchase #3 $100.37   13.832%   $114.2532   $114.25   $114.25   $114.30  
  Purchase #4 $184.99   9.301%   $202.1959   $202.20   $202.20   $202.20  
  Purchase #5 $203.83   12.168%   $228.632   $228.63   $228.65   $228.60  
  Purchase #6 $192.49   4.675%   $201.4889   $201.49   $201.50   $201.50  
  Purchase #7 $159.87   4.377%   $166.8675   $166.87   $166.85   $166.90  
  7 purchase totals = $1,259.24       $1,363.5423   $1,363.55   $1,363.55   $1,363.60