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 $22.92   4.573%   $23.9681   $23.97   $23.95   $24.00  
  Purchase #2 $197.25   3.164%   $203.491   $203.49   $203.50   $203.50  
  Purchase #3 $239.26   10.153%   $263.5521   $263.55   $263.55   $263.60  
  Purchase #4 $68.99   5.795%   $72.988   $72.99   $73.00   $73.00  
  Purchase #5 $96.51   10.207%   $106.3608   $106.36   $106.35   $106.40  
  Purchase #6 $125.83   10.478%   $139.0145   $139.01   $139.00   $139.00  
  Purchase #7 $221.27   10.668%   $244.8751   $244.88   $244.90   $244.90  
  7 purchase totals = $972.03       $1,054.2496   $1,054.25   $1,054.25   $1,054.40