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 $205.28   4.246%   $213.9962   $214.00   $214.00   $214.00  
  Purchase #2 $64.68   8.293%   $70.0439   $70.04   $70.05   $70.00  
  Purchase #3 $245.71   7.475%   $264.0768   $264.08   $264.10   $264.10  
  Purchase #4 $69.92   6.120%   $74.1991   $74.20   $74.20   $74.20  
  Purchase #5 $227.32   6.260%   $241.5502   $241.55   $241.55   $241.60  
  Purchase #6 $152.51   3.690%   $158.1376   $158.14   $158.15   $158.10  
  Purchase #7 $28.68   12.630%   $32.3023   $32.30   $32.30   $32.30  
  7 purchase totals = $994.10       $1,054.3061   $1,054.31   $1,054.35   $1,054.30