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 $95.26   11.746%   $106.4492   $106.45   $106.45   $106.40  
  Purchase #2 $153.92   7.226%   $165.0423   $165.04   $165.05   $165.00  
  Purchase #3 $244.82   8.208%   $264.9148   $264.91   $264.90   $264.90  
  Purchase #4 $174.85   9.200%   $190.9362   $190.94   $190.95   $190.90  
  Purchase #5 $122.76   11.309%   $136.6429   $136.64   $136.65   $136.60  
  Purchase #6 $149.40   5.466%   $157.5662   $157.57   $157.55   $157.60  
  Purchase #7 $134.96   7.201%   $144.6785   $144.68   $144.70   $144.70  
  7 purchase totals = $1,075.97       $1,166.2301   $1,166.23   $1,166.25   $1,166.10