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 $62.97   10.423%   $69.5334   $69.53   $69.55   $69.50  
  Purchase #2 $167.75   7.403%   $180.1685   $180.17   $180.15   $180.20  
  Purchase #3 $243.53   8.615%   $264.5101   $264.51   $264.50   $264.50  
  Purchase #4 $86.76   4.683%   $90.823   $90.82   $90.80   $90.80  
  Purchase #5 $145.99   6.241%   $155.1012   $155.10   $155.10   $155.10  
  Purchase #6 $110.40   4.442%   $115.304   $115.30   $115.30   $115.30  
  Purchase #7 $67.34   12.715%   $75.9023   $75.90   $75.90   $75.90  
  7 purchase totals = $884.74       $951.3425   $951.33   $951.30   $951.30