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 $61.95   6.390%   $65.9086   $65.91   $65.90   $65.90  
  Purchase #2 $188.81   3.359%   $195.1521   $195.15   $195.15   $195.20  
  Purchase #3 $192.82   11.558%   $215.1061   $215.11   $215.10   $215.10  
  Purchase #4 $221.34   12.486%   $248.9765   $248.98   $249.00   $249.00  
  Purchase #5 $196.94   3.357%   $203.5513   $203.55   $203.55   $203.60  
  Purchase #6 $37.30   13.502%   $42.3362   $42.34   $42.35   $42.30  
  Purchase #7 $56.99   9.364%   $62.3265   $62.33   $62.35   $62.30  
  7 purchase totals = $956.15       $1,033.3573   $1,033.37   $1,033.40   $1,033.40