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 $95.58   12.662%   $107.6823   $107.68   $107.70   $107.70  
  Purchase #2 $23.95   13.777%   $27.2496   $27.25   $27.25   $27.20  
  Purchase #3 $151.55   10.179%   $166.9763   $166.98   $167.00   $167.00  
  Purchase #4 $90.33   7.527%   $97.1291   $97.13   $97.15   $97.10  
  Purchase #5 $41.66   7.611%   $44.8307   $44.83   $44.85   $44.80  
  Purchase #6 $218.80   9.522%   $239.6341   $239.63   $239.65   $239.60  
  Purchase #7 $35.89   8.180%   $38.8258   $38.83   $38.85   $38.80  
  7 purchase totals = $657.76       $722.3279   $722.33   $722.45   $722.20