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 $81.79   5.852%   $86.5764   $86.58   $86.60   $86.60  
  Purchase #2 $115.39   6.854%   $123.2988   $123.30   $123.30   $123.30  
  Purchase #3 $157.95   11.435%   $176.0116   $176.01   $176.00   $176.00  
  Purchase #4 $235.61   10.144%   $259.5103   $259.51   $259.50   $259.50  
  Purchase #5 $5.33   3.658%   $5.525   $5.53   $5.55   $5.50  
  Purchase #6 $184.55   8.160%   $199.6093   $199.61   $199.60   $199.60  
  Purchase #7 $172.46   8.193%   $186.5896   $186.59   $186.60   $186.60  
  7 purchase totals = $953.08       $1,037.1210   $1,037.13   $1,037.15   $1,037.10