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 $115.68   9.171%   $126.289   $126.29   $126.30   $126.30  
  Purchase #2 $207.83   13.407%   $235.6938   $235.69   $235.70   $235.70  
  Purchase #3 $13.44   5.832%   $14.2238   $14.22   $14.20   $14.20  
  Purchase #4 $111.28   5.495%   $117.3948   $117.39   $117.40   $117.40  
  Purchase #5 $158.82   8.278%   $171.9671   $171.97   $171.95   $172.00  
  Purchase #6 $250.86   4.542%   $262.2541   $262.25   $262.25   $262.30  
  Purchase #7 $60.58   6.519%   $64.5292   $64.53   $64.55   $64.50  
  7 purchase totals = $918.49       $992.3518   $992.34   $992.35   $992.40