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 $86.97   10.395%   $96.0105   $96.01   $96.00   $96.00  
  Purchase #2 $18.33   11.258%   $20.3936   $20.39   $20.40   $20.40  
  Purchase #3 $53.44   12.304%   $60.0153   $60.02   $60.00   $60.00  
  Purchase #4 $208.42   4.336%   $217.4571   $217.46   $217.45   $217.50  
  Purchase #5 $187.80   5.572%   $198.2642   $198.26   $198.25   $198.30  
  Purchase #6 $174.66   7.566%   $187.8748   $187.87   $187.85   $187.90  
  Purchase #7 $240.82   11.312%   $268.0616   $268.06   $268.05   $268.10  
  7 purchase totals = $970.44       $1,048.0771   $1,048.07   $1,048.00   $1,048.20