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 $63.47   9.118%   $69.2572   $69.26   $69.25   $69.30  
  Purchase #2 $242.95   9.533%   $266.1104   $266.11   $266.10   $266.10  
  Purchase #3 $185.78   4.870%   $194.8275   $194.83   $194.85   $194.80  
  Purchase #4 $123.40   4.202%   $128.5853   $128.59   $128.60   $128.60  
  Purchase #5 $30.56   6.852%   $32.654   $32.65   $32.65   $32.70  
  Purchase #6 $25.54   6.798%   $27.2762   $27.28   $27.30   $27.30  
  Purchase #7 $62.88   5.589%   $66.3944   $66.39   $66.40   $66.40  
  7 purchase totals = $734.58       $785.1050   $785.11   $785.15   $785.20