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 $192.25   7.697%   $207.0475   $207.05   $207.05   $207.00  
  Purchase #2 $121.85   10.441%   $134.5724   $134.57   $134.55   $134.60  
  Purchase #3 $161.44   8.174%   $174.6361   $174.64   $174.65   $174.60  
  Purchase #4 $218.77   13.373%   $248.0261   $248.03   $248.05   $248.00  
  Purchase #5 $161.45   8.306%   $174.86   $174.86   $174.85   $174.90  
  Purchase #6 $95.62   7.325%   $102.6242   $102.62   $102.60   $102.60  
  Purchase #7 $36.68   10.844%   $40.6576   $40.66   $40.65   $40.70  
  7 purchase totals = $988.06       $1,082.4239   $1,082.43   $1,082.40   $1,082.40