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 $85.92   11.357%   $95.6779   $95.68   $95.70   $95.70  
  Purchase #2 $34.32   9.479%   $37.5732   $37.57   $37.55   $37.60  
  Purchase #3 $69.85   7.835%   $75.3227   $75.32   $75.30   $75.30  
  Purchase #4 $220.70   13.873%   $251.3177   $251.32   $251.30   $251.30  
  Purchase #5 $115.95   3.146%   $119.5978   $119.60   $119.60   $119.60  
  Purchase #6 $218.81   3.564%   $226.6084   $226.61   $226.60   $226.60  
  Purchase #7 $224.76   6.629%   $239.6593   $239.66   $239.65   $239.70  
  7 purchase totals = $970.31       $1,045.7570   $1,045.76   $1,045.70   $1,045.80