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 $56.59   10.132%   $62.3237   $62.32   $62.30   $62.30  
  Purchase #2 $81.31   6.164%   $86.3219   $86.32   $86.30   $86.30  
  Purchase #3 $45.87   5.546%   $48.414   $48.41   $48.40   $48.40  
  Purchase #4 $202.86   11.524%   $226.2376   $226.24   $226.25   $226.20  
  Purchase #5 $40.30   9.485%   $44.1225   $44.12   $44.10   $44.10  
  Purchase #6 $82.73   11.716%   $92.4226   $92.42   $92.40   $92.40  
  Purchase #7 $179.45   11.189%   $199.5287   $199.53   $199.55   $199.50  
  7 purchase totals = $689.11       $759.3710   $759.36   $759.30   $759.20