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 $41.84   3.434%   $43.2768   $43.28   $43.30   $43.30  
  Purchase #2 $80.95   4.352%   $84.4729   $84.47   $84.45   $84.50  
  Purchase #3 $213.54   11.578%   $238.2637   $238.26   $238.25   $238.30  
  Purchase #4 $112.98   3.827%   $117.3037   $117.30   $117.30   $117.30  
  Purchase #5 $192.86   10.333%   $212.7882   $212.79   $212.80   $212.80  
  Purchase #6 $189.32   4.867%   $198.5342   $198.53   $198.55   $198.50  
  Purchase #7 $119.59   12.342%   $134.3498   $134.35   $134.35   $134.30  
  7 purchase totals = $951.08       $1,028.9893   $1,028.98   $1,029.00   $1,029.00