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 $195.74   5.751%   $206.997   $207.00   $207.00   $207.00  
  Purchase #2 $58.81   4.758%   $61.6082   $61.61   $61.60   $61.60  
  Purchase #3 $126.66   5.213%   $133.2628   $133.26   $133.25   $133.30  
  Purchase #4 $168.97   7.806%   $182.1598   $182.16   $182.15   $182.20  
  Purchase #5 $152.94   11.603%   $170.6856   $170.69   $170.70   $170.70  
  Purchase #6 $157.97   4.654%   $165.3219   $165.32   $165.30   $165.30  
  Purchase #7 $203.51   10.384%   $224.6425   $224.64   $224.65   $224.60  
  7 purchase totals = $1,064.60       $1,144.6778   $1,144.68   $1,144.65   $1,144.70