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 $43.57   8.111%   $47.104   $47.10   $47.10   $47.10  
  Purchase #2 $208.39   7.483%   $223.9838   $223.98   $224.00   $224.00  
  Purchase #3 $145.48   8.853%   $158.3593   $158.36   $158.35   $158.40  
  Purchase #4 $218.71   5.324%   $230.3541   $230.35   $230.35   $230.40  
  Purchase #5 $141.68   8.777%   $154.1153   $154.12   $154.10   $154.10  
  Purchase #6 $24.54   8.131%   $26.5353   $26.54   $26.55   $26.50  
  Purchase #7 $186.83   7.567%   $200.9674   $200.97   $200.95   $201.00  
  7 purchase totals = $969.20       $1,041.4192   $1,041.42   $1,041.40   $1,041.50