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 $62.26   5.149%   $65.4658   $65.47   $65.45   $65.50  
  Purchase #2 $212.92   5.675%   $225.0032   $225.00   $225.00   $225.00  
  Purchase #3 $22.44   10.106%   $24.7078   $24.71   $24.70   $24.70  
  Purchase #4 $187.61   11.433%   $209.0595   $209.06   $209.05   $209.10  
  Purchase #5 $176.74   9.114%   $192.8481   $192.85   $192.85   $192.80  
  Purchase #6 $180.39   13.220%   $204.2376   $204.24   $204.25   $204.20  
  Purchase #7 $134.64   4.629%   $140.8725   $140.87   $140.85   $140.90  
  7 purchase totals = $977.00       $1,062.1945   $1,062.20   $1,062.15   $1,062.20