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 $233.79   3.338%   $241.5939   $241.59   $241.60   $241.60  
  Purchase #2 $57.97   9.188%   $63.2963   $63.30   $63.30   $63.30  
  Purchase #3 $39.92   11.422%   $44.4797   $44.48   $44.50   $44.50  
  Purchase #4 $78.83   11.746%   $88.0894   $88.09   $88.10   $88.10  
  Purchase #5 $242.90   4.560%   $253.9762   $253.98   $254.00   $254.00  
  Purchase #6 $185.96   7.796%   $200.4574   $200.46   $200.45   $200.50  
  Purchase #7 $214.55   8.630%   $233.0657   $233.07   $233.05   $233.10  
  7 purchase totals = $1,053.92       $1,124.9586   $1,124.97   $1,125.00   $1,125.10