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 $62.31   11.688%   $69.5928   $69.59   $69.60   $69.60  
  Purchase #2 $39.33   10.826%   $43.5879   $43.59   $43.60   $43.60  
  Purchase #3 $177.69   13.291%   $201.3068   $201.31   $201.30   $201.30  
  Purchase #4 $192.78   7.681%   $207.5874   $207.59   $207.60   $207.60  
  Purchase #5 $138.31   3.294%   $142.8659   $142.87   $142.85   $142.90  
  Purchase #6 $133.85   8.627%   $145.3972   $145.40   $145.40   $145.40  
  Purchase #7 $236.61   6.766%   $252.619   $252.62   $252.60   $252.60  
  7 purchase totals = $980.88       $1,062.9570   $1,062.97   $1,062.95   $1,063.00