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 $54.71   13.379%   $62.0297   $62.03   $62.05   $62.00  
  Purchase #2 $105.47   11.828%   $117.945   $117.95   $117.95   $117.90  
  Purchase #3 $220.77   7.292%   $236.8685   $236.87   $236.85   $236.90  
  Purchase #4 $177.91   13.482%   $201.8958   $201.90   $201.90   $201.90  
  Purchase #5 $142.51   7.288%   $152.8961   $152.90   $152.90   $152.90  
  Purchase #6 $124.58   6.306%   $132.436   $132.44   $132.45   $132.40  
  Purchase #7 $90.78   11.553%   $101.2678   $101.27   $101.25   $101.30  
  7 purchase totals = $916.73       $1,005.3389   $1,005.36   $1,005.35   $1,005.30