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 $29.54   13.614%   $33.5616   $33.56   $33.55   $33.60  
  Purchase #2 $186.85   10.444%   $206.3646   $206.36   $206.35   $206.40  
  Purchase #3 $96.64   7.523%   $103.9102   $103.91   $103.90   $103.90  
  Purchase #4 $200.31   3.546%   $207.413   $207.41   $207.40   $207.40  
  Purchase #5 $103.36   8.840%   $112.497   $112.50   $112.50   $112.50  
  Purchase #6 $219.97   13.353%   $249.3426   $249.34   $249.35   $249.30  
  Purchase #7 $204.26   8.522%   $221.667   $221.67   $221.65   $221.70  
  7 purchase totals = $1,040.93       $1,134.7560   $1,134.75   $1,134.70   $1,134.80