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 $212.35   11.651%   $237.0909   $237.09   $237.10   $237.10  
  Purchase #2 $44.80   12.828%   $50.5469   $50.55   $50.55   $50.50  
  Purchase #3 $48.86   8.617%   $53.0703   $53.07   $53.05   $53.10  
  Purchase #4 $188.86   9.264%   $206.356   $206.36   $206.35   $206.40  
  Purchase #5 $45.63   5.264%   $48.032   $48.03   $48.05   $48.00  
  Purchase #6 $103.91   5.532%   $109.6583   $109.66   $109.65   $109.70  
  Purchase #7 $48.50   9.535%   $53.1245   $53.12   $53.10   $53.10  
  7 purchase totals = $692.91       $757.8789   $757.88   $757.85   $757.90