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 $221.43   6.359%   $235.5107   $235.51   $235.50   $235.50  
  Purchase #2 $140.27   8.567%   $152.2869   $152.29   $152.30   $152.30  
  Purchase #3 $209.31   11.727%   $233.8558   $233.86   $233.85   $233.90  
  Purchase #4 $11.29   5.380%   $11.8974   $11.90   $11.90   $11.90  
  Purchase #5 $113.63   6.650%   $121.1864   $121.19   $121.20   $121.20  
  Purchase #6 $241.87   4.866%   $253.6394   $253.64   $253.65   $253.60  
  Purchase #7 $95.27   11.553%   $106.2765   $106.28   $106.30   $106.30  
  7 purchase totals = $1,033.07       $1,114.6531   $1,114.67   $1,114.70   $1,114.70