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 $65.87   7.706%   $70.9459   $70.95   $70.95   $70.90  
  Purchase #2 $114.85   5.841%   $121.5584   $121.56   $121.55   $121.60  
  Purchase #3 $106.99   3.315%   $110.5367   $110.54   $110.55   $110.50  
  Purchase #4 $234.89   10.431%   $259.3914   $259.39   $259.40   $259.40  
  Purchase #5 $149.97   6.765%   $160.1155   $160.12   $160.10   $160.10  
  Purchase #6 $232.32   8.591%   $252.2786   $252.28   $252.30   $252.30  
  Purchase #7 $190.69   5.542%   $201.258   $201.26   $201.25   $201.30  
  7 purchase totals = $1,095.58       $1,176.0845   $1,176.10   $1,176.10   $1,176.10