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 $216.43   13.641%   $245.9532   $245.95   $245.95   $246.00  
  Purchase #2 $178.81   12.745%   $201.5993   $201.60   $201.60   $201.60  
  Purchase #3 $165.41   12.749%   $186.4981   $186.50   $186.50   $186.50  
  Purchase #4 $51.54   9.560%   $56.4672   $56.47   $56.45   $56.50  
  Purchase #5 $217.70   5.426%   $229.5124   $229.51   $229.50   $229.50  
  Purchase #6 $45.52   6.346%   $48.4087   $48.41   $48.40   $48.40  
  Purchase #7 $177.40   4.463%   $185.3174   $185.32   $185.30   $185.30  
  7 purchase totals = $1,052.81       $1,153.7563   $1,153.76   $1,153.70   $1,153.80